I personally don't like that much the sound of a dirty slap tone. I think that you can get a better tone with a compressor or/and a tone enhancer pedal, like a preamp, or eq filter, or a boost, usually with a mid scoop. Some use chorus as well (check Mark King) to get some clank.
But that's just my personal taste.
I think the B7K is much more usefull with that because of the eq section. Another drive pedal that I've heard great slapping tones from is the Grizzly, but that's with the funkulator section only, with no drives.