Learned this one from my dad and grandmother. To preserve your paint brush, you will need oil(non food item) and paint thinner. Before the initial use, work a very small amount of oil into the bristles. Now, rinse it in paint thinner. After you are finished using the brush, clean it normally. Again, work a very small amount of oil into the bristles. Repeat this process, every time you use your brush. For added life, use paintbrush soap.

As a sign writer, as well as a modeller, using natural bristled brushes, I use petroleum jelly/Vaseline. It nourishes the bristles and helps to maintain their shape when set aside. Just use standard spirit cleaner to clean it off when you use them.

I use bridal tule (the netting a bride puts over her face) as a brush scrubber. It gets the paint out without having to mash the bristles, and then I clean it in mineral spirits or rubbing alcohol (depending on the paint I used). Been doing it for nearly 30 years and I still have some of the original brushes... I also tend to use Japanese ink brushes for fine work...they hold up far better than most others.