I will begin by stating that we are not professionals, but just watched some videos and decided to refinish two bedrooms in our home. Our local rental company proved sandpaper in 24, 36, and 80 grit. This is how we prepped our floors. We stained them with oil based Mocha then I saw a photo of light floors I loved so we ended up sanding them again. We went with Bona Natural Seal and Traffic HD. We did sand them again with 120 grit paper per the recommendation on the gallon, but this was by hand with a palm sander. We applied two coats sealer then one coat traffic HD, then we screen sanded with 180 grit I believe. There was a bit of grain raise due to the nature of water based products. After our second and final coat of Traffic HD, there was far less grain but there was still a texture. I'm not a professional. I do not know if water based is supposed to be glassy smooth like oil but ours is not. That said, we are very happy with the results! They are smooth underfoot, but there is texture when you feel with your hand. I do believe if we used a piece of equipment to sand the first 120 grit before the sealer, instead of a palm sander, it would have helped to reduce grain raise, and also, if we had used a piece of equipment between the two top coats, instead of a screen on a painters pole, it would have left a smoother finish for the final coat. We did 4 coats total. 24 grit drum sander (ds), 36 grit (ds), 80 grit (ds), 120 palm sander, 2 coats of Natural Seal, 1 coat of Traffic HD, sanded with pole and screen 180 grit, 1 coat of Traffic HD.
Hopefully this is helpful to someone else, just our experience!! Not that it is all the correct method.
But the product itself was very easy to apply. We used a t-bar that I purchased from a local flooring company, in person. He highly recommended that I use a roller instead for ease of use, but we really didn't have much issue with the t-bar. We have loved the Bona products!!