Both ways are ok, if you glue rifle from the start however you wont be able to paint its backside. Not that its needed much, it wont be visible anyway.
However there is a slight advantage of painting unglued, that will allow you do a batch painting of all your rifles and hands. Quite handy if you use airbrush for example.
The Dance of Death begins - embraces, caresses, and kisses,
The Harlequin loves you as you fall over in pieces!