How to do (sync) publishAndWait against a (async) process model?

I have a process model that is built with a async pub/sub model. But I now want to expose it a synchronous web service, by doing a publishAndWait for response.

From reading the doccos it seems I am forced to do a reply to use publishAndWait? If that is true, then my model, which automatically publishes (I presume with a publish not a reply) is unable to be invoked in a simply synhronous fashion.

Is there a way to get my model to reply. Or must I manually have to get my model to do a reply (rather than the automatic publish)?