I find with the Dry Treat products that different techniques work for different stones.
For example on Caithness Sandstone or other very porous surfaces we find that when using Dry Treat Enhance Plus or StainProof that a very thin coat of about 1/3 the prescribed application with a roller left overnight then applying the remaining 2/3rds as a heavy application left 2 hours then buffed off works best as a wet on wet washes the sealer too far into the tiles.
On polishd stone/tiles however a wet on wet approach is better then buffing off the excess.
With their water based products we would apply, allow to dry the apply a second coat.
In some cases we apply their water based sealer first as a primer coat followed by enhance plus then finishing with stain proof. This is rare due to the amount of time required as it is 24 hrs between each product. Usually we only do this type of work when this technique is specified by the architect and they want enhancing and the 15 year protection of the StainProof.
Overall my preference with water based fluoropolymer sealers is to apply, allow to dry then apply second coat. With alcohol or solvent based siloxanes like DryTreat StainProof and Enhance plus it varies with the stone/tile.