Self teaching formation flying and aerobatics can be done but it would be foolish to recommend it without knowing skill and dilligence of the pilot involved. That, no doubt, is why extreme caution has been urged by others on this thread.
I can only add that as with picking up any skill there are great advantages (including safety) to getting someone who has built up the skill to coach you.
I would advise against 'going it alone' and briefing and sensible leader all important when you practice.
A sensible leader who understands the issues can make the difference between an enjoyable session and an unpleasant experience.