Once I've got all the rivets in place I'll seal the models with at least 2 coats of Testors clear coat. After that I'll green stuff the mistakes. When working with paper and GS I've found that when sanding down the GS it will ruin the paper. To help keep this from happening I coat everything in at least 2 coats of clear coat first, then apply the GS and then sand it down. This way you sand down the GS even with the clear coat instead of wrecking the paper.
After that's done move on to base coating and painting like normal.