Does he actually have reflux? I know there is something referred to as silent reflux (my cousin had it, she was the HAPPIEST baby ever but projectile vomited after eating) but that usually involves really puking and not just dribbling spit up.
If it is reflux, slow down his eating. He needs to suck to sooth but try to feed a little and then take a break, burp, start over. Keep him upright for much longer than you'd think necessary and burp burp burp. Even when you're certain there can't be any more air in there, try one more time.
There are meds for reflux but really, if it's not interrupting his sleep, making him cranky, or hurting his weight gain - what's the point! They can be difficult to get down (weird grainy texture or horrible taste) and it's not easy to get the timing right.