Reading Deakin's articles is excellent advice from a general knowledge point of view but unless this particular engine also has Gamijectors/engine monitor some of the specific techniques won't be available to you. Having said that who, in their right mind, wouldn't have them fitted to a latish model T206?
If this aircraft is so fitted operate it exactly as John suggests as long as that is in accordance with the owner's wishes (I suppose). If not then reducing MP an inch/minute on descent won't hurt a thing but be aware than once you're down around 5000'/20 in MP then the turbo is not doing much and hasn't been for a little while. Its cooling nicely and you can leave it at 20 in until joining downwind and then bring it straight back to whatever setting is appropriate for speed reduction to Vfe and then leave it there - merely adding drag (flaps) as you curve around base and final - one last reduction to idle as you round out. I haven't flown a T206 since 1987 but if memory serves 12-15in MP on downwind.
Since the Turbo has been cooling and spinning down for the last part of the descent, the circuit and approach/landing, the coolest it will be is on touchdown. Every minute you spend sitting at idle on the ramp is just heating it back up again - and your pax.