Germinating peppers does not require sulfur. I have never used it. I often get 100% germination and often 2-3 faster than the expected time. The trick is moisture and temperature.

As far as using it later, I would imagine that depends on the specific nutrient situation. It might help some people and not help others.

Foilar spraying would of course need to be done on the underside of the leaf, but otherwise epsom salt is great where needed (and much cheaper than buying the same thing from garden centers)!