Caring for coarse coat

[CarolCorley]

I have a 21-month-old whom I'm hoping to show but I'm having coat problems. He has with a nice coarse coat and we have sandy Florida soil. What I'm finding is that the hair is breaking off, so no chops yet, and when I comb him out, I am getting rid of too much undercoat. I have a lot of tools, but should I be brushing him to condition the coat, and if so, what kind of brush? Is there a better way to keep the undercoat from matting that will allow him to develop a good full coat?
Also, I have been advised to bathe him weekly but I hesitate to because we (along with the rest of the State of Florida) fought a hard battle against fleas this year and I'm afraid to wash off the Advantix (Frontline quit working.)
Thanks,
Carol