I just did a quick test and found that Gunze Mr Masking Sol Neo will lift Tamiya acrylic… [sigh] Not sure what the base solvent is as it is odourless (and I can’t read Japanese). I did lay it on a bit thick though, and it took ages to dry, so perhaps it may work better when applied thinly.
On the other hand, a thin application of Humbrol Maskol didn’t have any visible effect, even though it has been reported to attack acrylic paints.
Silly Putty (or Play-Doh works, so I’m told) is rolled out and placed along the edges of the camo. It can be pressed into place for hard edge, or left as a roll for soft edge. There have been many threads on it. Here’s a search of “Silly Putty” on these forums:
I use Easy Mask from Micromark. As it dries clear, I tint it with a small quantity of pink/purple ( whatever comes as soon as it is very visible ) acrylic ink and it does not lift Tamiya paints. The Easy Mask does not smell of ammonia, unlike Humbrol Maskol. Only remember to put a “serious” coat, not too thin or you will not be able to take it out afterwards.