For decades I have had good Somali, Ethiopian and Eritrean friends of mine telling me to use mayonnaise in my hair. Finally, I decided to listen when I saw some on sale at Loblaws.
I bought some canola mayonnaise earlier this year and it is really good! The avocado one would have been better and I know this, but it was not on sale :-). You do have to just put it in and wash it out because as my neighbour Duncan says, you do not want animals chasing after your head :-). It does help to make your hair feel great though! It is especially good for mature locs, as well as well as unlocked hair.
You can use it between washing with shampoo and rinse out your hair and then use your usual conditioner plus the mayonnaise to extra condition the hair.
You can also go through your usual hair washing routine of a pre-hot oil treatment, shampoo, conditioner and use the mayonnaise at the end of the hair washing routine. Then, you can also apply your oils after you have thoroughly rinsed out your hair.
I have seen a lot online that if you are going to use mayonnaise in your hair that you should not use it more than once a month. I think this would depend on your hair type and also the time of year regarding the climate.
Regardless of how you use mayonnaise for your hair either dreadlocked or not, it is a great conditioner and will truly have your hair feeling silky.
I have been using the mayonnaise every time I wash my hair and it works just fine. I have mature dreadlocks/locs though.