I've bred a couple of sunfish species, and I don't think it's worth going to the trouble of putting mud in the bottom of your tank. If you condition them right, and get conditions right for them, then they should breed.
You don't say what part of the country you're from. It's been said that sunnies from a more northerly location need a cooling down period before they'll breed. Putting them out in a back yard pond that won't freeze solid will probably do just that.
If that's not possible, you might try keeping them in a dark tank in a dark room for two to three months.
After the cooling period/dark period turn the temperature up to the high 70s, increase day length to 12 or more hours per day, and feed them a lot. Females need to eat a lot before they'll ripen.
If you do that, they'll spawn in gravel. Peter Rollo has had blackbanded sunfish spawn in flower pots. I put square plastic tubs half filled with gravel in the tank and let them breed in the tubs.
Good luck.
I was thinking and i thought that i would have an easier time breeding sunfish if there was mud at the bottom of the tank to make it more natural. I found some stuff at the local pet store for reptiles that is an all natural sand and it looks just like mud but i want to know if my plants would grow in that situation. i am planning on starting a mud bottomed fish tank that wil be planted and have several pieces of drift wood and rocks and it will be 75 gallons. i have had years of expierience taking care of fish and i thought it might work.