You might want to post this on the Home Decorating forum.

Why? The question is absolutely about paint/stain.

OP didn't ask if anybody thought staining the posts a driftwood color would make the room look better, she just asked how to do it.

This is the 4th thread I've seen with the advice to post it on the Decorating Forum.

Fresca, I don't know that stain will stain *paint*;

if it does, it'll be opaque, like paint, & if it doesn't, your posts will be driftwood with a green undertone.

It seems to me that stain needs something it can penetrate, so...I'd sand them.

They'll be gorgeous.

Sylvia, I routinely suggest the Home Decorating forum because posts asking about color tend to get more responses over there, and some of the posters there might suggest a different approach than the specific question asked.

Many people who are new to GardenWeb post here asking for color advice, but few of the paint specialists here are colorists. Whereas, many of the color experts hang out in HD and don't read this forum. I have long thought that this forum should be called "Painting Techniques" or some such name.

Specifically for this question, I think there are several ways to go, one being a whitewash in a driftwood shade, which should make sanding unnecessary. But I don't have enough personal experience with the process to suggest it.