How to re-paint a garage door?

I have an existing garage door that I want to paint to match new grey Facias and soffits. Can anyone recommend the best method of application and materials to use. The door is currently white, not showing any signs of rust but does require a good clean and rubbing down.
Gary, August 2019


done
Is it steel? GRP? Aluminium? Plastic coated?

Nggf, August 2019
There are hundreds of paints on the market of both primers and gloss paints on the market.
Some websites are saying it if it's not rusty you don't need a primer, some say use an external gloss.
Some use rollers or paint brushes and some spray. I don't possess spray gun so would have to buy!
Can anyone suggest the best way forward for this?
Thanks in advance

Gary, August 2019
you can buy garage door paint

anon, August 2019