Olive oil ~ on unwashed (dry or lightly dampened) hair.  Because my hair is thick, I divide my hair in 4 sections by making 2 parts like this + and place each one in a clip to keep them divided.  One section at a time, I pour oil into my hand and smooth it through until the hair is soaked from scalp to ends.  (I estimate that I use about 1/4 cup in all.)  Then I comb it all and put it in a braid or bun and leave it at least several hours, usually overnight.  Wash and condition as usual.

 

Mayonaise ~ on freshly washed hair, usually after a clarifying or chelating wash, in place of normal conditioner.  While the hair is still wet, smear a bunch of mayo all through the hair concentrating on the ends.  Don't put much on the scalp area unless you have a very dry scalp.  Clip the hair up and wrap plastic wrap or a plastic bag around the hair area, wrap a warm towel around that (warmed in the dryer or something).  Leave it for an hour, then rinse thoroughly with warm water.  Air dry.  If it feels greasy the next day, I lightly shampoo it and condition.

 

Quicker method using conditioner ~ to be done in the shower.  Wet hair with hot water to open up the cuticle.  Slather on a bunch of conditioner all through the hair, I mean a bunch.  Clip it up in a bun trying not to squeeze out the conditioner.  Leave it while washing and shaving or whatever.  Rinse out the conditioner, then shampoo and condition as usual.

 

Feel free to alter it to best suit you and your hair type.  I'm sure others have different methods to add to what I've said.