Show off the voice, but sing funny. Sing against type, but play the type anyway. Let them know you know that they know you'd never be cast in this part in a million years. Be smart (but not smart-assed).
A man I worked with had the pale, thin (THIN--never skinny), non-muscular physique of the screaming sissy that he was. He also had a rich baritone. When auditioning he would go out there and give them butch--"My Defenses Are Down" from Annie Get Your Gun--and by doing that, telegraphed that he could not only do character roles, but also make beautiful noise.
He also on a dare, once sang I Hate Men (Kiss Me, Kate) with suggestive asides and in his baritone range.
He worked all the time because they thought (correctly) that they could throw a lot of things at him.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher