Garage Door

I need to re-paint my Henderson up and over garage door. I have started to scrape off the loose paint that has been on for about 18 years. I don't want to scrape all of it off, but would welcome advice on preparing for painting. I am assuming, rub the surface with glass paper to provide a key. wipe down with turps, spot undercoat where I have scraped down to the primer. Then paint top coat. Any improvements to suggest?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hammerite possibly?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A bit of a bugger to apply if I recall correctly. Also there won't be a colout to suit SWMBO (I guarantee)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.