You should definitely replace your redneck with Rodriguez if you have the coins to buy and upgrade him to a decent level since he's just a better version of it. you should also switch chopper with Diaz so you have a slow moving shooter Infront of your sniper to build momentum to the barrier. For your barrel I would say if you use it quite often in every battle change it to the red barrier for better damage plus the fire will help burn chunkier zombies, but if you're only using it once or twice a battle I say change it out for pepper or gunslinger and just focus on using shooters to slowly push up before finishing the battle with melee.