1. it is not necessary, but for decals too look nice, and if you want a different sheen to the one already there, you will need a gloss/matt/satin coat. for decals too look nice, and not have silvering(when it looks glossy and wierd, a gloss coat is necessary before application, and a coat of your choice after. also, model acrylic paints have a binder to them, which means that a later coat won't 'reactivate' the bottom coat.

2. it is not necessary to do that in my opinion (since it will take forever for a qtip), just wash it in warm soapy water, and put it in a glass cabinet, tupperware box,(anything dustproof basically).

3. put the parts together and apply the glue with a fine brush down the seam, and capillary action will do the rest, and squeeze hard, after a few seconds, you may notice some molten plastic ozzing out which has dried, just sand this down after. (this only works for really thin glue)

4. i could do a whole essay ont his, but here are the basics (you may want to research some more just type model washes on google) it is just really thinned down oil paint, 5% paint rest thinner, and apply it with a fine brush to the details, when dry, there may be a patch of the wash next to the line, remove it with a q tip MOISTENED not wet in thinner. it is best to do this on a gloss coat as capillary action helps the wash flow.

second number 4. just put glue on the part, and it should dissolve through the paint, then place it in and apply pressure.

5. read this following post http://www.scalemodelguide.com/painting-weathering/painting-guide/primers/

also, no the paint type does not matter, just make sure the paint has cured (24 h)

sorry for the long post, if you have anymore questions, i'm sure we'll be happy to help.  ;D ;D  good luck