I forgot how to use DMSO

When we cryopreserve cells, we add the cells into a solution containing DMSO and freeze them slowly. This is the basic method. However, I have used a special stock solution that permits the cells to be frozen quickly. I recently froze cells by using DMSO in the same method as the special stock solution. Then, all cells died. I forgot the basic method because I got used to use a useful special tool.