gravity5
+1y
Nice thing about using flat clear is you can buff them and they will stay flat....and they wont turn white from exposure like most primers.
If you are set on using a primer though PPG DP90 is an epoxy primer and it lays down super nice, plus once it has cured if you want a very low sheen on it you can wipe it down with tire shine and then wipe it dry....
And yes you can paint it later, just make sure to properly clean it first