I use 10:1 ratio with Meguiar's #00 as my wash. It is probably the most neutral, gentle wash I've used and does not eat up or dissolve the clay. It is often used for wet sanding too.
Whatever you use, you can try a 10:1 ratio. Or, you can use a waterless wash like ONR. On a side note, I have been using ONR diluted to a QD ratio and spray each panel before I dry with a MF. It adds gloss and reduces towel induced marring.