I've used UC over UC several times but always end up with a small bubble or two before I'm done. I'm not a perfectionist so I think they came out pretty good. Better than many ARFs I've seen. I apply the trim with minimal heat to avoid shrinking/warping the trim and go back over it several times later to keep it from coming up. The trim just seems to stick better for me after several heat cycles. Keep a stick pin handy to pop any bubbles that come up. Put the iron on them to get the air out and then immediately place a cool, wet wash cloth over the bubble firmly to stick it down. In the future, on models that I'm more particular about, I'll use the moneykote/windex method as mentioned by Campy.