Dremel Problems

okay so i went out and purchased a dremel router attachment and some router bits (expensive, why i dont know couldnt find them as individuals) I am having trouble with it to say the least. Im not sure if i should have just gone with the router table for my husbands router and used those kind of bits. They have more selections, its cheaper, but i already had the dremel and its lightweight. Im worried about doing many passes over a section to make it larger. the dremel bits are quite small and if im trying to make an epitaph or something like that then im worried about recking it once its done once. Also, do i cover the whole tombstone with putty or just the areas that i want to blend together. at 20 a sheet i dont like to waste thats why im practicing on my white leftover stryofoam. PLEASE...let me her how to work this thing im dying.