Drilling balls is a preference. As long as the span is correct, there is no wrong way of doing it. I've drilled balls fingers first and thumb first,.... felt the same to me. Drilled for other people,... could tell the difference of what order. IMO, drilling thumb first is a little easier, but the thumb is easy to drill anyways. Centerline, thumb span cut, drill! I dont bash anyone for drilling either way, so long as you get it right.
Boasting avg has nothing to do with drilling, it means JACK SQUAT what you avg. You can avg 250 on sport patterns but, if you cant hit a line, it wont make a difference. Throwing a ball and drilling a ball are two TOTALLY different things. I've been around guys that dont bowl or bowl 1 league a week but they are some of the best in the area. It's because they do so much business, they cant bowl.
Those who basement drill, how you stay in business and make a profit by undercutting brick and mortars is beyond me. But thats on you. Good luck and maybe it can turn into a legitimate business. A wise man told me, get paid what you're worth. If the shops in your area suck, then make money off there shortcomings in a legit way.