ged
xylene is a carrier / solvent , it is not a sealant.
do not roll seal flagstones as you will get awful edges where the excess runs and you will also get pooling.
the best thing to do is spray acrylic that has been at least 50/50 cut with xylene, and start on a part that does not show. they will have to be bone dry or you will get ghosting and no amount of overspraying will lift it out.
if they are yorkies they can be a nightmare
cheers