I know that Gandhi was involved in the civil rights movement in South Africa during he beginning of the 20th century, but was there a specific person, or group, that he learned how to protest through non-violent means?
While Indian traditions have certainly influenced Gandhi very much, one mustn't neglect the large influence that Western (broadly construed) thought had on him. For instance, he was very influenced by Tolstoy.
I am quoting the review of a new book that compares Gandhi to the Stoics:
Sorabji explains that Gandhi's biggest direct inspirations were John Ruskin's Unto this Last (1862), Tolstoy's The Kingdom of God Is Within You (1894), Christ's Sermon on the Mount, and Plato's Apology of Socrates which portrays Socrates as a soldier of truth fearlessly accepting death.
Gandhi was a student in London from 1888 to 1891. Parnell, the Irish leader, died in 1891. His tragic career suggested to Indian intellectuals that
1) Secret Societies and Assassinations were bound to strengthen the hand of the Imperial Police and provoke savage reprisals
2) The politics of 'boycott' could easily get out of hand and take a Communal (i.e. Sectarian) dimension while also setting the 'Classes' against the 'Masses'.
3) Westminster needed to have confidence that an avowal of Non-Violence was indeed genuine. Later, Gokhale, the Moderates, efforts in London were undermined by, his old class-mate, Tilak's Radical grass-roots activism.
4) Just as Parnell was undone by a sex-scandal, so too would any Mass Movement fall into disrepute if the charge of immorality could be levelled against its organizers or grass-roots workers
It was not just Ireland which provided this lesson. The 'Physical Force' Chartists had been crushed by Gen. Napier who pointed out that the Govt. not only had the physical force but the ruthlessness to use it. Still, the working class did get increasingly enfranchised as a result of intra-elite competition. Similarly, the 'Revolutionary' Socialists of the Hyndman type had failed to achieve anything while the 'Slowly-slowly' Fabians were impacting policy. Similar points might be made about the Trade Union, and later on, the Suffragette movements. Radicalism backed by Violence failed. So did hunger strikes and civil disobedience. However, Gandhi did not let anyone fast to death thus there was no need for an Indian version of the 'Cat and Mouse' act whereby a Suffragette would be released if her weight fell too much and rearrested later on. Forced feeding too was not needed in India.
In South Africa, the Chinese protested the Pass Law in the same manner as the Indians. However, the Chinese miners were deported so that Smuts and Botha could play the 'yellow peril' card while showing the Mine owners who was boss. When the Indian working class went on strike (against the poll tax which they genuinely couldn't afford), Smuts couldn't deport them because 1) unlike the Chinese they were British subjects- Britain would have had to resettle them 2) White workers also went on strike thus turning the problem from a 'Racial' to a 'Class' issue.
Gandhi's nephew coined the term satyagraha at a time when Gandhi was shrilly denouncing anyone who didn't go to jail and stay in jail to protest the Pass law. However, as soon as Gandhi himself went to Jail he did a deal with Smuts and came out within a few weeks. He now made an extraordinary claim0- viz that the Pass Law was a good thing. Indians should voluntarily carry a Pass and pay a discriminatory tax and so on because these are inherently good things. His only quarrel with Smuts, Gandhi said, was that Smuts had made the thing compulsory as if Asians were too stupid or vicious to see that being treated like a dog or a slave is actually a good thing. Gandhi was very badly beaten once he came out of prison because people suspected he'd taken money to betray his own people. This wasn't true. At this time 'satyagraha' became very important for Gandhi. He knew in his heart that he hadn't meant to betray his own people. Yet, clearly, his belief in his own genius could not be demonstrated in logical language. Thus 'satyagraha' became Gandhi's vehicle to feeling good about himself after he'd screwed up big time.
Again and again, Gandhi would jump feet first into any topical issue by declaring that everybody else who had done anything useful in the field was corrupt, stupid, evil and cowardly whereas he himself had the solution. He'd then recycle some simplistic nonsense and make great claims for it and link it to his magical idea of 'satyagraha' or 'swadesi' or 'swaraj' because he had shit-for-brains. A lot of money would then be collected and wasted in the most foolish possible manner. Still it provided good 'copy' as well as a Gesture Political Credential of a wholly corrupt kind.
I may mention that that the Jain/Hindu/Irish practice of going on hunger strike as a means of emotional blackmail was only used by Gandhi against Hindus or 'Low Caste' people. It had nothing to do with Non Cooperation or Civil Disobedience which, in any case, had a wholly Indian origin and tradition pre-dating Gandhi;s return to India by a decade. Thoreau may be mentioned in the context of not paying taxes- but that failed immediately and Gandhi didn't actually read much Thoreau. Ruskin has nothing to do with Civil Disobedience. Gandhi liked his stupid essay saying that you can pay your workers less if you pretend to love them in a Christ like way. Tolstoy/Chertkov's views on sex may have been important for Gandhi & Kallenbach but clearly neither engaged in mass political activity.
In conclusion- Gandhi's techniques were the same as that of other Moderate Indian lawyer politicians. He collected money, published a Journal, did a lot of networking, and trained a cadre of agitators who could 'fill up the jails' on demand. What set Gandhi apart was that he had a proven track record of 1) being ultra-loyal to the Brits and totally non-violent 2) being an utterly worthless negotiator adept at snatching defeat from the jaws of victory 3) getting a lot of money from wealthy Hindu industrialists
How did he achieve this? The answer is that he never stood for election. He believed Parliamentary Democracy to be Satanic and the moral equivalent of Prostitution. If for nothing else, Gandhi should get a statue in Westminster for this belief of his.
From understanding Gundhi learned his protest techniques by the Parihaka in New Zealand who did nonviolent protests before him.