I have the same problem you do and no type of cream or powder helped at all. Tagaderm and Bandaid blister pads have worked well, although when it is very hot they sometimes don't stay put on long rides. Lately I have been using liquid bandaid on the places that tend to chafe, and that has worked, but I haven't done any rides longer than 30 miles - might have to reapply. When the weather warms up a little more, I plan to begin my quest once again for a saddle. My Lady Diva Gel is comfortable everywhere else, but rubs those spots. I'm thinking maybe a Jett. I tried the Ruby, but it was too hard.
Grits
2010 Trek 5.2 Madone WSD, SI Diva Gel Flow
2002 Terry Classic, Terry Liberator