Back on Track(s) - AFV Centurion question...

Hi guys,
Been a while since I've done any modeling. Life and such gets in the way some times. I've got group build projects over due, about 5 models in various states of incompletion, its just a mess!

Instead of a WIP thread its basically a Work Almost Complete...a WAC, if you will....My father and I have a bit of a deal going. If he builds a model, I paint it. Since I have my own projects on the table, as well as a back log of his projects that I need to paint, I've got a small mountain of models in various stages. This, of course, is one of them. I think I got a bit overwhelmed by all I had unfinished which lent a hand in my recent lack of modeling motivation. Like the subject suggests, with this, hopefully I'm back on track...Any how, just want to put a pic up real quick and a question.

Question: what is the best glue for a metal barrel? Also, do I prime the barrel before painting?

Thanks!