Ideas on grouting tumbled marble?

We've been in the middle of a complete kitchen remodel for two months now. We're doing it all ourselves! Well, really just my husband since I'm out of commission since a surgery went bad three months ago (*sigh*). We brought the entire room down to studs (and even had to replace a few of those since my house is 110 years old!). The chimney stack is in the kitchen (no fireplace and the kitchen is only 10 X 12), I was hoping when we pulled off the *plywood* that was over it and painted and wallpapered how many times, that we would find red brick - no luck - just concrete. So, we tiled over it with 12 X 12 sheets of 2 x 2 tumbled marble squares. It looks great. Now my problem is this: I've read a few ideas on how to grout it without getting grout in all the little crevices and holes that give the stone its character - some say to seal it first and then grout and then seal again after cleaning. But to me that defeats the purpose of sealing since it would be a light 1st coat in order to not penetrate the grout lines (otherwise the grout would not stick), and then when you put the second coat on, it would not fully penetrate the stone to give it the water proof sealing it needs because the first coat would not allow it in. Ok, so others say to using painters tape and put a piece on each and every stone that I want to protect from getting "filled", then grout normally.
I was wondering if anyone had experience with grouting tumbled marble and can tell me what you did.