I did it! I didn't want to do the duct tape one but since I had to do it by myself, it was easier. The trick for anyone doing it on themselves is a bit of flexibility and a large mirror. For the back, the best thing to do is to go horizontally up to the bra strap then vertically from the shoulder down to the waist for the upper back with long pieces of tape. You will have gaps but since duct tape keeps its shape, you can fill the gaps when you remove it. Of course you'll have to cut it from the front but this won't affect the shape as long as you do it correctly in the front.

Anyway, I hope that helps for anyone that doesn't have a helper. Plus, it's a bit of a workout so make sure you have plenty of water near and a good air conditioner! Oh and if you don't know how to get the goo off of your scissors, soaking them a bit in any kind of oil will clean off the glue residue.