Before committing to glue, check that the parts fit together by doing a dryfit. Give the mating joints a swipe with sandpaper to smooth it out and remove any unwanted flash. If any misalignment, you will need to correct it first which may involve some surgery. Minor gaps can be taken care of after glue is applied. Major gaps may need to be tackled differently.
- If using liquid cement (eg. Tamiya green cap), just put the two parts together and use the provided brush to apply a touch of cement to the joint. Capillary action will draw the glue into the joint and that is usually strong enough once dried. For long joints like fuselages, do this a couple inches at a time until all joints are sealed. Sand off any glue residue. If gaps are still present, fill with putty or superglue and sand to perfection from 400 to 1200 grit.
This tutorial should be able to give you some guidance as well
http://z12.invisionfree.com/ScaleModelsMal...?showtopic=4760- If using thick cement (eg. Tamiya white cap), just apply a bit of glue along one or both sides of the mating joints and then put the parts together. Sand off any glue residue. If gaps are still present, fill with putty or superglue and sand to perfection from 400 to 1200 grit.
Be careful with using rubber bands to hold the fuselage together. If you put liquid cement near where the band is, capillary action will draw the cement around the band and thus around the fuselage or whatever part it was you banded together.
HTH
cheers and happy modelling