hi unrestored , i stripped back all the old paint by hand ie flapper wheels , and disc's but i used a couple of disc's which were to harsh and left scratches in the metal which i didn't realise i had done so when it came time to prep for paint we had to do alot more work to ensure the scratches were filled before final primer sealer.
Once I cleaned the surface of all of old paint went over it with prepsol ( wax and grease remover) then sprayed on a coat of etch primer .
couple of hints put your prepsol in a pump up spray bottle(small one) like what you you use to put weed killer in hardware store have them about $20 . that way you can spray on wipe off , dont use the same rag twice , ie dont wipe back over the area just cleaned with the same rag as you will just re contaminate the area .
wear fine rubber gloves but make sure no talc powder inside them , the gloves stops you putting oil from your skin on the surface .
the etch primer, does what the name implies etches into surface giving you a foundation for all that will happen later on , if you sprayed a primer surfacer on it could and most likely would lift undoing all your hard work .
Go to your local paint shop and have a yak to them they will help , i didnt paint mine my mate did and told me off ! about the scratches
hope this helps
cheers shane