36 grit will remove the paint but does rough up the metal. But any less grit and you'll work yourself to death getting the paint off.
After using the 36, you can DA the metal with 80 and it's ready for epoxy primer.
If you use chemical stripper, you still want to DA the metal with 80 before the epoxy.
I prefer to chemical stripper as it's hard to get in tight places with a grinder.
You could do a combination of both. Grind your flat places and chemical strip the rest.