What are the best application techniques for slate sealer to ensure maximum protection and longevity of the surface?

The best application technique for slate sealer to ensure maximum protection and longevity of the surface is to first clean the slate thoroughly, apply the sealer evenly using a brush or roller, allow it to dry completely between coats, and apply multiple thin coats rather than one thick coat. This will help the sealer penetrate the slate effectively and provide a strong protective barrier against stains and damage.