Yeah, I think whiter would look better. The full size set pieces as well as the CGI assets look very white (almost with a semi-glossy, or "enameled" type of sheen) Very different from the flatter, tanner/greyer whites of the Star Wars universe
I used Micro Mask before. It's not bad, but it can have problem with water based paints. I have used it with Tamiya paints and find it can be hard to come off, but not too bad. I generally put it on really thick to help it come off easier. Also I let the paint coats full dry and cure between applications. it worked nicely for my Slave-1