The layer is nearly 1/4". The thinset IS the grout. After the tile is "stuck" fairly (2 hours or so depending) well, you apply another layer of the the special thinset for between the tiles mixed a bit thinner with a rubber/trowel/squeegee. That's it! Be careful to not let it dry fully before you squeegee it.
Cleanup just before filling the pool with 5:1 muriatic acid. Not much to cleanup at all.
The special thinset is a modified latex with some special stuff in it because of the sun/heat here to help curing. It is used everywhere here. Made in Costa Rica.