Paul
Just a word to the wise, when I'm painting a model and It's usually a boat I always make up a couple of, in my case formica squares, covered with the same paints that I have sprayed on the model with notes written on the back. One I keep as a master and the other one I masked up and used to either paint with subsequent layers before painting the boat and then the master or in your case I would use it to see if the paint is effected by any other process, i.e., in your case meths or thinners, can be a bit of a pain when you just want to crash on but saves a lot of heart ache later.
Re the Trimline tape I am still using tape that Is 3 years old, I store it at room temperature in its box. As others have said apply it without stretching especially over moulded parts and when you go round corners. takes of bit of practice.
Paul.