@MechTechThanks! Interesting idea about baking soda and filler, I'll look into that! Yup, the main issue was the pegs on the parts were too thick, and needed to be thinned out some in the 3D program, in order to fit nicely together. This was printed at 1/285 scale.
It was hard to get any of the resin parts to stick to one another using any types of glues, which explains the glue mess.