Liquid Mask

Second for MicroMask, easy on and off, no residue to clean, plain old Scotch removable tape or Tamiya tape gets it with no damage to paint. If it's an older bottle it may be a bit thick and stiff, a bit of water as needed stirred in returns it to original state.

It's quite clear, not so easy to see the edge when applying. A bit of dark blue food color stirred in helps to make it more visible. It's been around for a long time, I like it.

I've found Mr. Masking Sol R to be very useful in filling holes or covering areas that will be cemented. Once it's dry, it can be removed easily with the tip of a pointed X-Acto blade or sharp tweezers. If you will be cutting the masking material, be sure that the blade you use is very sharp — otherwise it may drag the mask right off the plastic. 

There are two or maybe three different formulations. This is the one I use:

Bob Ingraham

Vancouver

I use Micro mask. Though i must say i am not a huge fan of liquid masks. I have found them ok when filling in gaps in paper mask sets, but useing them as the only mask i have found them awkward to remove without scratching the clear parts or removing paint from the area i wanted the paint on.