Hey Bones,
Well, what I know about tanks wouldn't fill a thimble, so I'll let someone else answer that question.
Now as to masking, if you're looking to make "blob" camo (not the official name, but it works for me), camo that has no defined straight edges or any of that stuff, try using silly putty. It can be oddly shaped like liquid mask, but it cleans up a lot easier and doesn't effect the paint.
-Fred