Tempera Paints for Making Washes?

So, I do a lot of hobby crafting for tabletop gaming that involves painting miniatures and building scenery (think model railroad hobbyists). In this craft, there is a lot of need for washes of different sorts that fill in crevices and crannies for developing shadowing and texture. I have some tempera paints that were gifted to me, but I don’t have much of a use for them and was thinking I could make them into washes of different colors since they are already very thin. Has anyone tried tempera paints for this? Will the paint hold up if painted over with acrylics? Will they be washed away when I attempt to seal my work (usually with Mod Podge and/or polycrylic)? I suppose I can experiment a little bit, but I thought I’d see if anyone else has attempted this before putting time into it.