First, if you are using an oil or a gel, and then putting the conditioner on on top of one or both, this technique will not work. The oil or gel sort of cancels out the work the conditioner needs to do in your hair, and your hair won't clump very well. It's best to wash your hair, and then use the conditioner directly. If you want extra conditioning, smooth a bit of oil over your hair at night, after your hair is dry and already has the conditioner in it.

Another thing is that this technique of leaving in the conditioner won't work with any conditioner (and especially not on top of heavy oils or gels). Some have sticky ingredients (similar ingredients to those in gels and hairsprays), which will build up and get crunchy and sticky. Some have very damaging ingredients like ammonium xylenesulfonate. Others are too light, and won't help at all. It's best to use the ones I recommend on my site because they don't have those types of ingredients that build up or hurt your hair. As long as the conditioner is okay, then it's okay to leave it in your hair. Some conditioners have salt in them (used as a cheap thickener). That's fine if you are going to rinse it out of your hair, but would be bad to leave in your hair. None of the conditioners I recommend for leaving in your hair have salt. Some other types of conditioner aren't slippery enough, so the force needed to get a comb or Denman though our thick curls will damage it.