Use dry cat food with seafood in it. It's cheaper that way because most of your bait will be eaten by cats and skunks and believe me you don't want to shoot a skunk. I tried hot dogs, canned (wet) cat food, sardines etc. but it was getting expensive because 80% of it was eaten by cats and skunks. Right now I use a 16lb bag that I got for like $8 at at Walmart. It's last a very long time (keep it sealed). It 's a combination of tuna, salmon and other seafood but Ed is right, coons will eat just about anything, even bread, leftover pizza.. save the bones & fat after you have steak, pork chops or chicken, or any dinner leftovers. They 'll eat it.
If you 're going to use the Whisper I would pick a range no more than 25yds, 20yds preferrably. Raccoons are large animals and tough. You miss the brain and they 'll easily walk away before you get another shot. Place a target or paper where the bait is going to be, and practice enough until you can get really good groups consistently and know you can put that pellet within 1/2" every time.
I have taken probably 100 critters from my home windows. Groundhogs and racoons are the most challenging because they have excellent hearing unlike the skunks & possums and spook very easily. You have to be prepared to shoot when they come, and not open the window or move stuff around to get ready if you have a high success rate. They 'll pick up the slightest sound and take off even if they are 40, 50yds out. I keep the window open all the time at night in another room when I use the outdoor sensor. I also keep that door closed which I have oiled well so it doesn't squeak when I open it. So keep the receiver in a different room because it's kind of loud, and cock the gun there too before you approach the window you shoot from. It's tough if you only have 1 room to work with. Cock the gun slowly and quietly. Keep the receiver under the covers to muffle the sound and turn it off immediately when it goes off. Then hopefully you can open the window without making any sound at all and your floor doesn't squeak. Also make sure you have a clear path to the window with nothing on the floor. I have spooked a couple of critters by stepping on my son's toys or other crap my wife threw in that guest room after I set it all up for the night.. The word is "silence". If you can accomplish that, you 'll get your racoon. Good luck.