Using Micro Mask For Masking Camouflage

I'm building the Tamiya M2A2 Bradley ODS, and have gotten to the point of absolutely needing to paint it (NATO camouflage, using Tamiya Acrylic Paints) before I can go any farther. I've been hearing and reading about Micro Mask, so I decided to give it a try. But, I first tried it on an old Monogram AV-8B that I built just for paint practice. This plane has no paint on it. I applied some Micro Mask to selected spots on a horizontal stabilizer, let it dry for a day, then applied some paint. I let that dry for a day, then removed the Micro Mask. I was extremely pleased!! Nice, sharp demarcation lines where the masking was. So, I painted the Bradley overall NATO Green (3 coats), let that dry for a few days, then masked certain areas according the Tamiya painting guide in the instructions, let the masking dry for a day, applied the NATO Brown paint, let it dry for two days, then masked again, let the masking dry for a day, then applied NATO Black (which looks like a very dark green to me, by the way). I let that dry for a while, and then decided to peel off all of the masking. Much to my dismay, some of the NATO Green (first color applied) is coming off with the masking, along with some of the NATO Brown. Is using Micro Mask on flat paint the wrong thing to do? Or, does it have to do with the paint being acrylic? When I used it on the Harrier with no paint, it worked just fine. Maybe this stuff should be used for canopies only, or areas where there is no paint?