"Free" mixing paletes....
I have found a good source of disposable paletes for mixing filler (I use "ICING" a two part thin auto body filler) or brush paint. Your local building supply store has samples of counter top laminate (Formica or other brands) Just ask for the obsolete samples. I got a chain with over 200 2.5"X1.75" samples.
When done with one, I just toss it. They are the right size and more important, THE RIGHT PRICE!!!!!!
As George used to say, "Free is good"
(FITTER knows of who I speak...)
Rick