The wipe on isn't as durable as the fast drying. You are doing something wrong if fast dry has bubbles when dry. Let's see if I can figure out the trouble.
Do you consider yourself a good painter? ( Why? )
Are you useing a high quility brush desighned for oil varnish? ( Not alll expenspensive brushes do well with all finishes)
Are you properly cleaning your brush after every use? (How?)
Are you laying down the film while working from a wet edge and not rebrushing holidays in finish?
Are you pouring finish from factory container into a dedicated application container? Are you disposing of left over finish from each application? ( Tell me why this is reccomended )
Are you tacking off before each coat? ( Type of tack? )
Are you maintaining clean air while finish is wet? ( How? )
If that is more effort than you believe nessary,just wait and there will be one or more counter-posters that agree with you and offer a simple solution. Still determined to learn refinishing and willing to work at it? I am willing to help you get started.

Not bubbles....dust - sorry....been staining and poly'ing for about 2 weeks and I think the fumes are getting to me (not really....I'm wearing a respirator the entire time I'm at the house.) I think my problem is a combination of dust in the air and the fact that I wasn't using a separate container (didn't even think about that, but know better) Did another coat tonight before we left - turned the furnace off so there's no air movement and sanded the old dust spots way down before re-applying. I clean my brush VERY well - vacuum and use a tack cloth after sanding (and then wipe with tack again immediately before applying the poly) I'm not a novice, but definitely not a professional, I know it's not a quick & easy process. Hopefully when I get to the house in the morning I will be happier with my results.

I believe you are on the right track with controlling dust. It is difficult but possible. The realization of possible trouble gos a long way. If there is still nibs in it tomorrow.try straining some finish through a nylon hose unless you buy a new can. I would probily leave the nibs if despite best efforts they presist. After all they certainly arn't as critical as on a table top.
In the name of learning,try this with your brush if there are nibs tomorrow. The least amount of poly allowed to dry in the brush will crack off bristils and create dust next time it's used. Whack the dry bristils across your hand or a fixed object similar to while shaking cleaner out after washing. If you do it in strong light,you might be amazed how much dry poly dust comes out of the brush.

Between cats and kids I've long since given up on achieving a dust-free environment and a perfect finish off the brush. Depending on the project I either live with a few nibs or rub the finish out after it dried to achieve a very good final result. Depending on the sheen desired you can rub out with anything from 0000 steel wool, pumice and rottenstone, to auto finishing compounds. A mirror polish on a long run of stairs would be a fair amount of work, but 0000 steel wool leaves a very nice surface and is pretty easy to do.

Just an update - I got them finished...and they will have to do :) Sometimes I need to go a little easier on myself and trying to do everything perfectly. FEET are going to walk on these every day, lol!! Nobody is going to notice a speck of dust in the finish!! I'm happy with them now! They're darker than the picture...poplar...stained to match our walnut floor that runs throughout the main floor. Just wishing I would have done poplar risers too - but we can change them later.