Tail find on bombs/armaments

You could try making a jig to align them properly, normally I just do my best and eyeball it.  However, I will usually apply glue to fin and body join area, attach, let it sit for a minute, then adjust till they're perfect, you could do the same with the aforementioned jig.

Sometimes with that kind of thing it's best to do one at a time. Like one fin a day, letting it dry before the next one. Otherwise you'll just end up pushing around a bunch of "wet" parts.