The flooring expert ever think about "why" they get rough surface finish? It is all due to their sanding, not sanding the wood smooth or even enough.

If, you sanded the floors to 120 grit or better, you're fine. The sanding needs to be thorough and even, no missed spots. Uneven sanding and missed spots will result in rough patches. I water pop all wood species when applying stain.

Here is a carriage house project we did in 2013.

White pine floors water popped and finished with Bona Dri-fast stain Spice brown (equivalent to Minwax English Chestnut), top coated with Bona Woodline Satin. Same recommended process, that I have been giving you .

Your work is the most beautiful!! I wish I could hire you to do my floors.

I will water pop mine regardless of his advice as the color just looks more uniform that way.

My flooring guys didn't sand exactly right with their machines, they left chatter marks and messed up the edges a bit. But I hired someone else and after the previous guys did everything with machines up to 180 grit, we hand sanded every inch of the floor to 120 grit...literally by hand with sand blocks. It was grueling, but at this point, I'm just trying to get it good enough so we can finish. I know it won't be as quality as it would be if I was doing it back in USA with the right equipment. And that's fine, I need to cut my losses and get it as best as I can.

Should I apply 3 coats of poly? And should I sand between? Will that smooth out the roughness of the raised grain from the water popping?

Apply three coats, sand in between each coat. Do not sand too aggressive for the second coat. You can be more aggressive for the following Coat. If, you feel that the coating is too thin after the third coat, apply a forth.

This sanding process will remove the raised grain.

Im on it! Will let you know the result when done. :-)

You're on the right track. Of course the floor will be a bit fuzzy after water popping. That's the whole point. It should make the stain color darker and more uniform, which can be an issue with Pine. We always apply three coats of finish after water pop and stain.