Can any verb be turned a reflexive?

Yes, in principle that's possible. Some verbs are only available in a reflexive version, some others change meaning, so you have all possibilities. But in general you can turn a non-reflexive verb into a reflexive one by applying the verb's action to the subject of the sentence itself. In English you'll find words like each other or myself, yourself, etc. that indicate the reflexive nature of the action.

non reflexive: Nous parlons à nos amis. -- We talk to our friends.
reflexive: Nous nous parlons. -- We talk to each other.

In Le Passé Composé, the reflexive version uses être instead of avoir:

Nous avons parlé à nos amis. -- We talked to our friends.

Nous nous sommes parlés -- We talked to ourselves.