[Closed] Painting a garage door

Brush is better than spray can for that size of job , unless you use a proper spray gun and the know how , + over spray risks getting on everything.
If I had a garage door to paint I would use something like Tractol , tough and easy , and wait till a day where you can do it after some rain has kept the dust down , and no wind.

I brushed on Sandtex exterior paint of garage doors about 10 - 12 years ago.

Needs redoing this year. Not bad, but I'm fussy.

Its true, the Sandtex 10 year warranty as written on the can does work.

Its oil based, none of this water based paint crap.

Brushed on really 'creamy'.

Good preparation is the key though. Lots of priming, sanding down, re-priming, sanding down. Just like painting a car really.

As mentioned before, choose a still day. Splash water on the ground to keep dust down.

Just used sandtex also, really good paint. Excellent finish everywhere i bothered to prep it properly, missed a couple of bits lower down which werent great so prep is key. Id heatgun and strip the entire door rather than sanding if i did it again.

One coat of the primer then 2 of the paint for me.

Zinsser All Coat Exterior waterbased. is superb. It's available in matt, satin or gloss. Is self priming and undercoating and can be mixed in any colour. It's a great drop of paint. I'm currently refurbing some old GPO phone boxes, 2 coats and they look amazing.

I used a brush + hammerite garage door paint (just wired brushed dodgy parts of the existing paint and washed it down, dried then painted). Still looks OK 19 years later

Short-pile roller (and lay off with a brush if you prefer that finish)
Johnstone's exterior paint

Quite by chance I started repainting ours this morning. I trawled the interweb for suggestions. I then went down to our local paint and paper shop. I spoke to a real live person in the trade.

He was quite honest and said that he would happily sell me all the fancy paints available. He stocks them. For me??? Preparation, preparation, preparation (as T B Liar nearly said).

Rub it down with 80 grade sand paper and remove all loose and flaking bits. Rub down again with 120 grade to smooth the surface and give a good key. Undercoat. Roller or brush is personal choice. Makes no effective difference.
Coat of gloss. Rub down lightly with 240 grade paper. 2nd coat of gloss. Ordinary oil based paint. Nothing fancy. Do it well and should last 10 years.

Ergo I'm just waiting for the heat to go out of the day then undercoat will be on.