Chuck the balancer fit is very tight and shouldn't need any sealer to prevent leaks. You can however use a little silicone grease on the crank and inside the bore of the balancer hub to ease the installation.
Don't forget to put some lithium grease on the inside lip of the front seal and the the outside of the hub to prevent a dry start on the seal.
The correct way is with an installer remover tool, and a light lubricating oil. It doesn't hurt to clean the snout of the crank of any paint over spray, and remove any burrs.
If your rubber ringed harmonic balancer is falling apart replace it immediately. Do not attempt to force the rubber back in with silicone spray. It will fail spectacularly, at the most inopportune time otherwise.