True. In most cases of using oil stains and finishes, it is best to do your coloring and clear coating in separate steps. By mixing stains into finishes, it upsets the proven formulations. Adding colorants to clears is best
Doing slurry grain fill is normally done with clears. Doing with stains defeats the purpose,as most all the pigment will be removed during the process. The slurry fill is to prep the surface for an even stain application over it
I forgot to mention this, but, thinking about Danish Oil is what provoked my question. I was watching and reading stuff about oil finishes. I've read of people doing a slurry grain fill with Watco Danish Oil Dark Walnut. Someone posted their recipe for their "Danish Oil" finish. Plus, I've seen how people dye figured maple, using sanding to pile the dye into the figure for contrast in between multiple coats of alchhol or water based dye. So, I thought, "what if I mix a dark Minwax Oil stain with an oil based varnish, maybe some BLO, maybe some naphta, plus japan dryer?" Would it dry? Could I just use is for a base coat or sanding slurry and build up a clear on top for protection?
If using it as a slurry, wouldn't the color pool in the grain and pores of something like mahogany, oak, or ash? Or beat up pine? Especially if I use a black stain?
I was not thinking too much about how it would look at this stage as far as an attractive look is concerned. I was mostly focused on mechanical issues such as drying, peeling, cracking, turning to cancer pudding, or otherwise just not working in any mechanical sense. I expected some color to be left behind so that it would act as a grain high light maybe, and with BLO in the mix, possibly an amber hue or glow.
BTW, I like this look (although not crazy about the gouges in the wood):
Apparently, Charles Niel would categorize that as blotchy. But to me it's not blothcy if it follows the grain and does not obscure it. If color contrast happens because of the grain lines and is gradual where there is no grain line then it's not what I would call blotchy. It's not uniform, but also not blotchy, if grain makes the difference.