Been processing my own venison and aging it in coolers for over 30 years. Wet aging venison in coolers works fine when done right.

• Step 1 is a quick and clean kill shot. A "light's out" shot prevents adrenaline from being released into the bloodstream. Adrenaline gives meat a strong gamey flavor.
• Step 2 - gut it and cool the meat ASAP. I much prefer a skinning rack. Less chance of dirt and other contaminants on the meat. Best to hang the deer, gut, rinse with clean water, and debone all in one spot.
• Step 3 - layer deboned meat in coolers. It is fine for meat to be completely surrounded in ice. Keep the cooler constantly draining so blood doesn't pool in the bottom. Start with about 4" of ice in the bottom, then add a layer of meat, and so on. Top it off with ice. A 48 quart cooler will easily hold 1-2 deer deboned. If in doubt, use an extra cooler and be overly generous with ice.
• Step 4 - tilt the cooler and keep the drain plug open at all times. Melting ice will help rinse the meat and flush blood out the drain hole. Check it daily to make sure the drain is not obstructed. Top the cooler off as needed to keep a good layer of ice on top.
• Step 5 - let it age. At least 7-10 days for best results.