I would recommend finding a therapist who is skilled in Mulligan joint mobilization techniques. In my experience as a physio I've had great success when treating both acute and chronic ankle sprains with posterior glides of the distal tib-fib joint at the lateral malleolus (in layman's terms gently pushing the bone on the outside of the ankle posteriorly).

Mulligan suggests that when you sprain the outside of the ankle (lateral inversion sprain) the fibula moves forward in relation to the tibia at the ankle joint. From what I've heard (I'm by no means a Mulligan expert) Mulligan theorizes that the swelling that occurs when you sprain the ankle in this way is primarily due to this bone being "subluxed" anteriorly.

Once I've mobilized the joint in this way and having regained some degree of ankle dorsiflexion (the movement of your ankle when the top of the foot moves towards your head) I usually tape the ankle in a similar way to the Mulligan technique, which can be seen on video here. I then follow this with exercises - range of motion, strengthening and so on.