Matt - that tire is truly in tough shape. You can try silicone spray, but if it will cure that tire it will take a while. If you are going to try silicone, really wet down the tires, wipe them down to clean the tires, wait a day and then wet them again, then repeat until you see improvement. It would be very interesting to see if silicone can restore the wider cracks in tires that that dry. I'm thinking you will see some improvement, but to entirely close those wider gaps may be wishing. I'm sure the smaller cracks will close up after a while. The healing process takes a while. If you try silicone, you won't be alone, I'll still be around to read everyone's reactions.
If you get some improvement after a few days (a week or so) and can saw with them, then you are on your way to eventual smooth, softer tires.
I wouldn't saw with wet tires. You don't want wet silicone on the saw blade. The stuff has to penetrate and leave the tire a bit darker color, but dry to the feel, instead of greasy.
The brand of silicone spray is not important. Just ask at the hardware or auto supply store for spray silicone.
We (at least I) would be interested in what you plan to do.
P.S. I'd give it a try, you can only improve them with silicone. You can't hurt them! Your only loss would be a buck or two and some time.
Best Wishes!!
Octogenarian's have an earned right to be a curmudgeon.
Chuck in Lancaster, CA