This is the one mod that is not even close to cost effective on this watch. That being said I've only bushed two and it took me just under three hours for each one. If you cut corners you'll end up with a crooked crown and probably a damp movement.
My best advice is to think about how fragile the threads are when you get any screw down crown. Make sure they have a light coating of oil and just close until contact is made. Rotating slightly counterclockwise as you start also helps.