Hi Snooze
Well it took about 2 mins to get them like that, but that's because I'm and OCD car freak and never let them get too dirty
Achieving it depends on how bad they are to start, but as I think I said to Yabot, if they've got a lot of carbon deposit, start with a bit of fine grade 000 steel wool and some metal polish. If they're not that bad then just polish on a microfibre.
One thing I often do, pre wash, is give them a squirt of Bilberry Wheel cleaner at same time I do my wheels and let that dwell, then normal wash followed by the polish stage and final buff with a fresh mf.
I've tried both Autosol and Auto Finesse metal polish but neither come close to Mothers Mag & Aluminium Polish. You will need to really work the polish in with the cloth or wool to remove the soot. If using steel wool be careful as it can cause unsightly scratches (mine have a few).
Once you've got them up to a decent state, a regular wash and polish with Mothers (buffed off with a very soft microfibre) should keep them looking tip top