[zennmotion]

I am a (too) enthusiastic DIYer, and I did this very thing- installed tongue and groove on a living room ceiling that originally had a $h!tty popcorn texture plaster that was done poorly, and then water stained.

It looks good now, 10 yrs later but I would definitely not do it again- super laborious with precision cutting, pre-staining (we just used ceiling paint, stain would be worse). The ceiling first had to be leveled using lathing strips, major pain. Then, once installed the wood (pine) continued to shrink and small gaps opened between planks- newby mistake. I let the boards (thin 1/4" strips) continue to dry and settle on what size they finally were to be after a year and essentially pulled down and reinstalled. Never again. I should have just installed 1/4" drywall over the popcorn plaster and be done. You could even put tin ceiling tiles over that if you want an interesting retro ceiling.

And if you're determined to try it, and you're using pine, I would not stain it at all. Clear polyurethane varnish will age to a very nice golden yellow color after a year or so. We have this on a porch ceiling (glutton for punishment, but I used old material that was thoroughly dried so it was a little easier and I was less fussy on an exterior porch) Any stain will eventually darken and look bad- I've seen plenty of 70s era man-cave/dens with pine paneling while house hunting and it's always dark and dirty looking if stained. And unlike paint, the stain color cannot be renewed/refreshed.