Wrap your paint brushes for later use:
I recently had a big project that required two coats of five different colors of paint. Instead of painting one color at a time I painted 2-3 colors a day to speed up the process. Rather than wash the brushes after every use, I wrapped each brush in plastic wrap, put them in a zipper bag and put them in the refrigerator until I was ready to use them again. The paint was still wet on the brush and it was just as fresh as the first time I used it.
It will stay that way for quite a while but if you aren’t able to get back to your project right away, you can stick them in the freezer. Just allow enough time to thaw them out before using them. Only do this with water based paints as I would imagine that oil paint’s strong smell would permeate the refrigerator. I have been doing this for decades and it sure saves a lot of time. Besides, I hate cleaning brushes.
Don’t let your paint dry up in the can:
When storing paint to use in the future, I put a sheet of plastic wrap between the can and its cover so the paint doesn’t dry up. When you scrape your brush against the can to get the excess paint off, some remains in the groove and when it dries then the cover never fits back on tightly. The plastic wrap seals the can so the air doesn’t get in and the top of the paint will not get hard. I used to throw a lot of expensive paint away after only one use until I learned this trick.