I had about 200 lbs of rock that i had in a pail of salt water for some time. I then decided to start cooking the rock, because the rock was in a dark pail, the cleaning process had begun and a lot of the gunk was already coming off.
what I did was to replace that water with some fresh salt water and add a cheap skimmer, I then added two cups of vodka and two teaspoons of brightwells Microbacter 7.what I got in the next two days was the most disgusting smell I had witnessed in a long time. Have you ever heard of how the human body decomposes after death, and how horrible the smell can be, well what I just described was a walk in the park after the grass has been cut. by the fourth day the smell was horrendous, the skimmer had taken a lot of crap out, but the vodka and bacterial dose had cleaned this rock amazingly. I did several water changes after that and I also pressure washed the rock the final stage was another bath in a pail of saltwater, half cup of vodka and two teaspoons of microbacter 7. The rock is in an excellent clean state, and without all the phosphates and algae that had accumilated over the years of being in other tanks.
This process was something I read on RC and did just to make sure that i could get the most clean rock I could. I thought it was clean after cooking it in the dark with saltwater and a skimmer. wow was I wrong. Give it a try you won't be disappointed. By the way don't leave the pail in the house, even with it covered the smell was escaping and permeating the house.
good luck.