There was a thread somewhere with details about a method of adding trim called "the Windex Method"
Anyone know where that thread is?
Anyway, Monokote is notorious for outgassing when heated. Over balsa it is not too bad because the wood can absorb some of the gasses but when putting additional coats of monokote over existing monokote it can be difficult to avoid bubbling.
Windex is another way of activating the glue on monokote.
Basically when adding trim you spray the area with windex, position the monokote and squegee out any extra liquid and bubbles with something soft like a scrap piece of balsa.