I don't like HETT, either! It didn't have enough hold besides being drying.
CO-washing more does not mean more product buildup. CO-washing more actually means cleansing your hair more, but adding more moisture at the same time! As long as you scrub your scalp well (since the thing you're cleaning your head with is the friction from your fingers) and really rinse everything out, you shouldn't have a problem with product buildup, unless you go way overboard on gels and stylers and leave too much conditioner in your hair.