The important thing is making sure for longer rides like this is you keep everything CLEAN and I do mean clean. Sometimes I will take a baby wipe in the middle of the day and wipe everything down there and then reapply my Bike Glide (from Body Glide) and if I know I am touring for days I will bring multiple bibs so I can wear one and wash one. I did say bibs and I think those are very helpful because they keep everything in place however cleanliness is super important. I chafe easily without much provocation but my Bike Glide and cleanliness helps greatly and for those long rides bib shorts are crucial.

I will say this may not solve everything you may have a different issue but I would certainly try this and see if it helps. I don't tour without baby wipes and ideally something that is 99% water or very low in chemicals. You might also consider after cleaning and drying before the night and before putting on some good moisture wicking undies like ExOfficio Give and Go using something to help with that I use cortisone cream but I have heard great things about using tea tree oil or even some good lotion can help.