again i agree with tiles as probably the best material for your garage floor as long as you use the correct tiles and do proper preparation .
standard grout is all you require and should finish almost flush with the tile surface.
epoxy grout is very expensive material and application will take considerably longer than cement based grout .
epoxy grout has specific applications , areas where hygiene is imperative or chemicals not compatible with standard grout .
as Le Mans X5 says , sealant can be applied .
as for good tilers being worth their wieght in gold , i have a buddy earning £2000 a day such is the quality of his work , he is one of the elite,a true craftsman .