I like 1/2 oz of unrefined shea butter mixed with 1/2 oz olive oil in a plastic tint bottle. I set the bottle in a plastic cup of hot tap water. I dampen my hair with warm water a bit by placing my hands under the faucet, then running them through my hair.
When the oil mixture is heated, I shake the bottle to mix the contents. I apply it to my scalp area first, then my ends, then on the rest of the length of my hair. After massaging it in, I comb it through. I put on a plastic conditioner cap, then a plastic grocery shopping bag, then my satin scarf. I make sure to cover my pillows with cases that I don't mind messing up, but the oil has never leaked onto them.
The total amount of the mixture (1 oz) is enough to cover my hair (thick, waist-length), so a little goes along way. When I first apply the mixture, my hair is not dripping wet, but is nicely coated. However, by the time I wash it out the next morning, my body heat, the plastic and scarf have made the mixture penetrate the hair more, and it is soaking wet. I apply a bit of shampoo to my hair before adding water because the oil mixture would be hard to rinse out if I applied the water first.
I have only done this sporadically in the past, but would like to start doing it twice a month. I hope I will be disciplined enough to keep it up.
ETA: I looked at my applicator bottle and I might be using just a bit more than an ounce of oil mixture. I try to be sure that I have equal parts of shea butter and olive oil, though.