I use scotch-brite pads to scuff up my hardwood jobs, cheap and abrasive enough. Even being brand new it has a risk of having many things already bonded to it. I usually strip the clear off to coat floors. Is it 3/4 or engineered or prefinished sealed wood? Used to be able to get some poly that was like armor back in the 60's / 70's. Everything back then was like that, course it was bad for you and everything else but it was tough and lasted longer.
While I do and have done lots of hardwood, I am not entirely sure to be honest about your question. I'll ask the floor guy who has been doing it a long ass time when I run into him about it. I see him usually every week.
Edit- I guess I could answer the other part.
After you scuff up the floor, use a tack cloth to clean it and get everything up. Work from a corner of a room out make sure to clean it VERY well. I turn off the AC/Heat during this to keep from stirring up more dust. Every spec of dust is a tiny little spot in the clear. You will never do a 100% perfect job but it will be fine and professional if this step is done right.
You apply most with a lamb's wool pad on a painters pole. I mix my clear up good and pour it in a pan for this , coat with grain one side to other in rows of 1-2 feet at a time.
Wear a headband to keep sweat down. If you start to sweat to point of dripping, finish the room you are in, switch shirts, dry off with a towel, swipe over the last run in a doorway and continue on.
Putting on Poly is easy as pie. Depending on the type you can recoat in 4 to 8 hours or next morning. Some new ones don't even require you to scuff between coats as long as it has been before a certain time.
If you don't mind taping up the shoe/base with blue tape you can skip the cut in, otherwise take up shoe mold before you do it, use a disposable bristle brush and cut in a 3-4 inch strip away from baseboard around the room before you use the pad. Very important to do this as fast as you can and get to padding room, or it becomes tacky.
Step back during all this at times and look at the sheen from a angle off the light. Make sure you have no big drips, ponding, or areas complete dry.
It really is easy, just want to make sure you know all the steps.