Qui est-ce que un peintre?

[Kawaii_Nequam]

Qui est-ce que un peintre? Un bon peintre?  

[iiJ o a]

You could ask that question in a better way:

" Qui est un peintre? Un bon peintre? "

Because your question is incomplete in the sense that you'd be asking: "Who a painter? A good painter?"
Well you are missing the verb, which would certainly be "is" to make the sentence more understandable.