Which is proper did is or did was?

Answer 1

NEITHER! "To be" is an irregular verbs which does not need the auxiliary DO to form it's Interrogative and Negative forms. The Interrogative is simply formed by changing places between Predicate (Verb) and Subject (the INVERSION).

She is Shelley.

Is she Shelley?

We are tired.

Are we tired?

They were in Kent.

Were they in Kent?

The book was interesting.

Was the book interesting?

Regular verbs form the Interrogative of the Present Simple with the auxiliary DO/DOES, while the Past Simple Interrogative requires DID.

Answer 2

The proper use is "did was." For example: "I thought he did was very kind."