Never heard of a stain blocking paint. There are paints that claim to be a primer and topcoat with two coats, but nothing that I would trust to block stains.
There are solid color oil and latex stains that look like paint to most people and they are effective for cedar and other tannin heavy woods.
There are solid color oil and latex stains that look like paint to most people and they are effective for cedar and other tannin heavy woods.