Boo,
When you wrote, "...seeing as they're coming off again, to do a brake overhaul.. pistons as well!...", I assumed you were having to replace the pistons for some reason. My mistake...
A Mity-Vac is a hand operated vacuum pump that, with a bleeding cup attachment, can be used to bleed cantankerous brake systems. But, like you, I usually dangle a chunk of hose into a jar with a little fluid in the bottom and pump away.