Awful garage door - how best to tackle?

[mousemoose]

See (hopefully) attached pic... garage door is peeling in very thick flakes... what is the right way to tackle it (sandpaper? Electric sander?) and what is the best dark grey paint to use on it?

Bump. Poor, sad, flaking garage.

That wants a good rub down with a wire brush on the rust and then painting with Hammerite.

Weirdly there is no rust, but layers of red and brown paint - still a wire brush I need?

Ah it looked like rust. Is it a metal door?
Get flakes off with a brush. Sand it with sandpaper to key it and then a good outdoor paint should do it.

Don't use Hammerite - it doesn't properly get rid of rust. Use rust remover and wire wool. I bought rust remover from Halfords. Then you can use a suitable primer and an exterior gloss or satinwood paint.

I think it's the red paint under the white which is showing in the OP's photo.

That doesn't look that bad. Just give it a rub down with some rough sandpaper and then give it a couple of coats of new paint.