Potions of master thievery
this is about as good as you are going to get for now. You can also cast detect traps (Minsc and Aerie I believe have it) and knock spells. Imoen does suck as a thief, but unfortunately there is not much to do. I used her throughout the chapter 4&5 and made it through alive so it is not undoable
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Never try to teach a pig to sing; it wastes your time and it annoys the pig
I've got to admit it's getting better, it's getting better all the time