I've built a couple of Coampell's kits and always start by staining all the wood parts with Driftwood stain. THat way, they have some color under the glue. Any glue will seal the wood and prevent stain from penetrating. For really old weathered unfinished wood, I then paint a light coat of flat white and then use lots (and I mean lots) of varying costs of india ink wash. I use a really small brush and apply it board by board to get varying degrees of gray. For weathered paint, I apply a couple of light coats of whatever volor I'm using and then use a plastic bristle brush in a rotary tool to wear some of it away. Check out my home page for some pics.
Doc