I commend your enthusiasm for attempting the repair.
Don't get testy, but let me ask...do you have a high end BMW recommended body shop near you? It's impressive what they can do.
As an aside, I had my front door painted by a painter that started out over thirty-years ago as an auto body painter (
http://coloralchemist.com/ ).
He spent over a month painting my door so we had a lot of discussion about painting and auto body.
It's just that a pro can repair your slight defects with ease. When you see a good painter do his thing, it's years of training and natural talent.