For those places, I can actually use a milder deodorant. Strangely enough. Can you try (on a weekend, perhaps) using a lemon or Thai Crystal Rock? I have had success with Thai Crystal Rock in there areas, even in the hot sun. It's not the same as other crystal rocks deodorants, they simply don't work on me..
Also, what do you use to shower? I'd think a low pH soap would be helpful...
I tried a homemade remedy. It was terrible and it's because they have a measured formula. It's proprietary and if they told you, they'd have to kidnap you, haha. It really is why they only tell you the ingredients, not the measurements. For homemade deos, you really just have to do some trial and error to see what works for you. I used baking soda and coconut oil. No bueno.