Tonight I was brushing some oil based enamel and polyurethane varnish on a small model and I didn't have any thinner or turpentine handy to clean the brushes -- I also wanted to avoid stinking up the house with solvents, especially in winter when windows are closed. Then there's also the matter of dealing with open containers of leftover solvent once the brush is clean. And the expense nowadays.
It ocurred to me to try what was available in the kitchen:
1.) first drying most of the paint off the bristles by squeezing with a paper towel, and then adding a few drops of salad oil to the brush. I tamped the brush well to mix oil and remaining paint, which actually worked just like a thinner.
2.) Then I added a few drops of dishwashing soap to emulsify the paint/salad oil mix.
3.) Then rinsed the brush with hot water.
It worked perfectly! The brush was squeeky clean, there was no mess, no odor, and the amount of "cleaning materials" was tiny -- a few drops of comon kitchen items. Drying the brush with a paper towel was all that was needed, and the bristles were shiny like new. In fact I think the oil and dish soap are probably kinder to the brush than sitting in refined petroleum products would have been.
Now this was a small brush, and not something to paint a room wiith and this method may be practical mainly for brushes 1-1/2" and smaller. But it really did work extremely well, so I though I'd pass it on.