Glossing woodwork...

[Parsnip]

Gents, I need some help.

In the process of doing up the house at the moment - the skirting and all other bits of interior wood (bannister, loft access etc.) are a horrid dark stain colour - it isn't paint as such, looks like a low sheen coloured varnish.

So far have done 2 bedrooms, painting the woodwork gloss white. Next is the living room, dining room and 2 landings, which will need to be done in one go - no separating doors to let me do a bit at a time, so it will be a huuuuuge job.

For the bedrooms, I settled on:
Plenty of sanding, coat of primer then 2 coats of gloss (Dulux one coat - one coat my arse!)
Experimented with sanding, 2 off primer and 1 off gloss, but it didn't quite get 100% coverage (annoyingly close...)

Is there a cleverer way of doing it? (I got shouted down when suggesting I do a few more days offshore on the next hitch to pay for a pro to do it - its more rewarding this way apparently...) Is primer straight onto the old finish (it isn't glossy, but has a wee bit of sheen to it) to save sanding a good idea? Or will this give a horrible finish?

I have contemplated removing the skirting, but for the sake of a few hours extra having to mask around the wood, I think I would do more damage taking it off and putting it back on.

The other elephant in the room is the bannister - its a spindly affair and I know I will resort to sanding it with a claw hammer eventually - any tips? Seriously considering just removing and replacing it.