I would normally downhaul on the beach, but make adjustment while on the water. It is always easiest to downhaul when the main is sheeted, so best if crew can do it. Racers loosen the downhaul at the weather mark and re-tension at the leeward mark.

Sheet the main while pulling the downhaul. Usually the harder you sheet the more downhaul will be needed. Light air loose, heavy air tighter.

New class rules allow a 6:1 too.