Windex only works if the top layer is monokote as the amonia lighly ativates the monokote glue. If you are putting ultracote on as the second color try using a trim iron set to low heat. ultracote adhears at a very low tempurature like about 160-170. Done like this , if you go slow, you will get no bubbles with ultracote. If you are putting monokote on then do the windex method, but don't ever put any heat over it.

Windex doesn't activate ultracote glue.

With monokote and ultracote you can also use trim solvent. If you use trim solvent, very, very, VERY little is needed. Play with scrap pieces befor you attempt the good one. When I use trim solvent I will get the piece of trim covering in perfect place and then use tiney pieces of tape put on in the middle of the piece of covering to hold it in place then I will lift one side, apply the trim solvent with a small piece of toilet paper and then I will hold the covering lightly tight on a 45 degree and I will quickly wipe/apply the covering with my index finger working across the half area, then remove the tape and do the other side. Works great if done right with very few bubbles if any at all. If you use too much trim solvent the glue will stay activated forever and be goopy and squishy.

I prefer to use ultracote with a low heat iron. Works the best!! I did all of the yellow this way on my last Ultimate build. No bubbles at all http://www.rcuniverse.com/forum/m_9018718/tm.htm