Is it advisable to put a second coat on grout joints using 511
Impregnator? I noticed on the can the statement that "a second coat
may be necessary for some surfaces". I am only going over grout
joints (about one hour's work this afternoon) but I had a difficult
time determining if I was getting sealer on all of the grout (the clear
sealer just did not show up real well on the grout joints).

My wife does 2 coats of AquaMix grout sealer annually in our tile shower
and two coats on the countertops.

I ended up using a toothbrush to brush the sealer on the quarter-inch grout
joints.

BTW, she uses a real boar bristle paint brush (which has better
absorption/carrying properties IMO than a nylon toothbrush)

We do use 511 as a sealer on our granite island.