Deep litter or deep bedding? For deep litter, the bedding needs to be in contact with soil. Deep litter does need changed every couple months, but shouldn't be too smelly with that size coop and only 4 birds. Is the coop well ventilated?
I have a poop board under my roosting bar with sweet pdz in it, take a kitty litter scoop and scoop out the poop every morning. I saw the idea on someone else's post here on BYC, makes a world of difference and I don't have a stinky coop! My coop floor is covered with Bermuda hay, works great. Hope that helps.
I use deep litter~not deep bedding~and it doesn't have to have contact with the soil, FWIW, so if you want to try a deep litter system, it will work on a wooden floor too, just takes a bit longer. I never clean out the coop until I need the compost for my garden or my head is touching the ceiling, whatever comes first. No smell, absolutely no flies, just lovely composting litter that smells like dirt.