I stained my deck with an 100% acrylic latex deck stain. Can I apply a clear sealer over the deck stain or a low sheen varnish?

Our home is 2 years old. The problem I am having is with the red wood railing around the deck. Most of the sapping has stopped but the paint is still chipping. I am using Sherwin Williams quick seal 350 hs alkyd stain blocker primer which is supposed to block

I stained my deck two days ago. I applied it with a paint roller. When I was done I was doing research and read that you should go over everything with a brush. So I started to put a second coat on. It is the summer and was getting really