Try some SLIME. No need to remove tire, just squeeze it in. If that doesn't work, then go to the tube. Have gone this route multiple times.
Bead sealer works great for leaks around the rim/bead, must break bead on both sides, clean and apply sealer.
Berryman’s tire sealer works great for dry rot.
Plugs when it is one or two punctures.
Tubes work fine until you hit a nail, etc., then you have a flat tire that needs to be plugged.
Removing and installing front zero turn tires is very difficult without a tire machine. $20-$25 per tire is about the current going rate.
I use a spray bottle with soapy water to find leaks in tires.