Hmm, the only use of a cheese slurry I'm familiar with is to inoculate the milk with a mold, namely blue penicillin or white penicillin types. Generally the lactic-acid starter bacteria are pretty much dead in the finished, aged cheese, so a slurry would not introduce the requisite starter bacteria to the milk. You still need the frozen cultures, mother culture/bulk starter, leftover whey, etc, for that. Plus, with a slurry, you also risk introducing any host of other bacteria, molds, and yeast into the milk, so proceed with caution.