dry sticky paint spoilt plasterbd wall texture

I was putting a new coat of paint on my internal plasterboard wall, and the paint it kinda old and a bit dry(sticky). It ended up with droplets and uneven texture.
The next day, I bought a new can of paint(darker colour) and paint over it, but now the spoilt texture is still showing thru.

I think I may need to sand the spoilt areas? But with some parts with thick paint and droplets showing, how am I gonna do it?

Is there such a thing as an electronic sander?

What am i gonna do?
Tricky one. Plasterboard is very hard to sand. Once you damage the paper cover it gets very rough. You'll probably need to go over the damaged bit post-sanding with some plasterboard joint fill and then sand *that*.
1 sand with med, paper you know the stuff, its in a roll usually yellow,
2, two coats of sealer undercoat,
3, and three coats of paint.
4, stick the lesson under your hat for next time , and worry about important things, ;)
Are you using a gloss paint.

If its that bad you might have to go for a flat finish which has good properties
in hiding bad painting jobs.
But if its intended to be rented out a full flat finish is not the best,as it marks