How can I paint glossy walls?

https://www.doityourself.com/stry/how-to-paint-over-high-gloss-paint

https://www.youtube.com/watch?v=ROkR8zql5bg

Hi Jayne, follow these instructions and they should help you with this,

https://www.doityourself.com/stry/how-to-paint-over-high-gloss-paint

The biggest problem will be the color change. It may take 2-3 coats to handle the color change. The gloss itself shouldn't cause much issue as long as as you are using latex over latex. If the paint is really dark or bright, you could use a bit of Kilz on your walls first. It doesn't need to cover thoroughly, just a thin coat over everything will allow the color change to go smoothly

I would prime it instead and then paint the walls with a lower sheen.

Prime with Zinsser or Kilz2. Then you should be good to paint. I was able to paint (2 coats) over a semi-gloss room with Behr Marquee.