I'd say never try to get something to do something it wasn't meant to do. If airbrushes were meant to have things flow back into them, they'd have a flow reverse valve built into them you could switch to, like a vacuum with both the sucking and blowing options.
I've never seen an airbrush with a suction option so I take that as my message that nothing was meant to go through it that way.
Just send your cleaner through the airbrush the same way the paint goes and make sure you don't let the paint start setting inside it before you clean it.
Backflushing should not be neccesary, ever.