When using a liquid mask make sure that you paint it on the area(s) to be protected fairly thick. If you don't, the mask will be a real bear to remove. Learned this the hard way. Often I'll paint on at least three thick coats of mask and let it dry throughly. Then do my paint work.
If you are nervous about opening doors on the actual model, then I suggest getting a cheap model and practice on that one. This way you will get the feel of opening doors and if you make a mistake all you would lose is time and perhaps the practice model. Never ever use your actual model as a so-called testbed!
Also, the smart thing to do along with using a scrape model is follow Mr. Obsessives advice. If there is one guy who knows how things are to be done, it is Mr. Obsessive.
Ok, I almost bought into this one. Here we see what looks like a model of the Ford 9000 but the details are too good to be true! Even photo etched parts don't look that good. What I think he did was build a really great background diorama and just parked a real customized Ford 9000 in such a position as to make it look like a model.
Either that or it is one heck of a beautiful piece of work!