We are looking at re-painting stair rails etc. Can we use WBP on top of gloss? If so what would be the process
Done the same a few months back on the stairs, doors and skirting over oil based gloss Light sand with 120 grit and then Zinsser 123 to give a good key, followed by two coats of Dulux water based eggshell worked for me. Astra (the pro) will be along to confirm or not, maybe different suggestion.
You can use some wb gloss over old yellow oil gloss paint but most need primer. I use adhesion primers all the time. Just think it's better practice to undercoat. Sand and a real good clean before you undercoat is important
Doing my own stairs at the moment, I'm using Crown Trade FastFlow undercoat followed by FastFlow gloss over old oil base paint, FastFlow is a hybrid paint and will go over old oil base paint with no trouble at all after initial preparation. Just completed painting a large 4 bedroom converted coach house using FastFlow over the old oil base paints, stuck like a dream! . Another paint is Johnstones Aqua but I prefer the FastFlow as it has more body to the paint.