So depending on what look you are going for, check this out, based on using clear AquaCoat grain filler(get from Rockler or Amazon), note the Optional steps depending on what you want.
https://aquacoat.com/pages/expert-wood-finishing-tips

and videos: https://aquacoat.com/pages/videos

 

Since you're doing test boards (smart man), try one with some Pore-O-Pac natural oil filler and tint it with your stain. Wipe in the filler across the grain, level it with a scraper and then it'll be a breeze to sand it smooth in a few hours so you can apply stain to the wood.

 

Thanks gents. I tried a very unmeasured glob of the gel stain in the Z-Poxy finishing resin (great stuff). So far, I'd have to call this an unqualified success. The first picture shows half of the board with straight Z-Poxy and the other half tinted. You can see the difference in the grain fill. The second pic has a wash of the gel stain over both halves of the board. It doesn't show the grain difference as much in the shot but it is there and much closer to just the stain on raw wood.

At least as important, the tinted Z-Poxy dried really hard. Sanded back with 320 and given the back-of-the-fingernail test it worked well with a single application. So, FWIW, it worked for me and I hope this might help anyone else considering using these products on a porous wood. Cheers, sh

 

I used Aquacoat on my last table build, which was Sapele so very open grain. I stained first, then filled the grain and sanded it back to level before applying clear top coat. No issues sanding through the stain.