Oak Banister and stringers

It would take a heck of a lot of sanding to get down to raw wood again but if you have the time, go for it. There are other options though.You could sand it lightly with 220 and apply a gel stain and poly.

Do not use polyshade for anything!!! Unless your into to a blotchy finish.
Going to have to sand off all the old poly, any left behind will not except the stain.
Use a gel stain not liquid for more control.
Tape off or cover anything you do not want the stain on, there's a reason they call it stain.
It's to each there own but I like the look of a wipe on poly. Main thing I like is instead of having to sand it all off and start off when it wears off unlike a reguler poly I can just wipe some more on.

This is not an easy thing for a DIY- but it is possible to tint coats of poly ( not the pretinted stuff- but custom made on the spot), and layer it up to make it darker.
This is by far the easiest solution - but is not unskilled.

I have a job coming up to do exactly this, and I will use Zar Ultra Max (waterborne Alkyd poly) and use transtints for color.

If I got all the poly off I can just gel stain over then rub on poly?

You have no idea how hard it will be to remove the coating.
Very hard.
And if the wood is sealed- it will not accept a stain into it- it would just lay on top.

You make a great point. I think I'm going to run some trials and then see what works. Where do you get the stuff you were speaking of brush jockey?

You think it will be that hard just to get the poly off? What about strippers (not the kind that take their clothes off) to remove the poly the sand the stain then poly?

I believe Brushjockey has offered you the best solution.Don't know why I didn't think of it, although I have used gel stain over a sanded poly and polyurethane over the gel stain with very good results.

I did some searching and I can't get that product in Canada. I am also a little unclear of the steps that would be involved even if I could get zar's.

That's the skilled part. might be worthwhile to find a pro that can do it.