That depends on the skill and what mats and stuffs there. For example, when I started twisting, I learned by trial and error. But when I started double backs off bars, I'd drill timers onto higher surfaces, then when I was ready, I threw one into the pit, it was a success, so thats how I learned that. However, when I learned tsuks, I had spot for a while. At my gym, we have a rule that you can't get spotted on beam, you have to work your way up, because spotting on beam causes fears. What happens when you needed a coach to just "be there", and you move up, and start learning bhs and you can't do a bwo on your own. Do you get what I'm saying?
It all depends on how comfortable the gymnast is with the skill after drilling it a lot.