If you have the time, once the wheels are clean - you can remove them, one at a time and carefully spray silicone sealant (available cheapest from Screwfix) on the alloy surface. This will do exactly the same job as the Autoglym sealant (wouldn't be too surprised if it were the same stuff) and leave a very slippery surface on the metal - hence the brake dust will build up less easily. Given that the silicone must never be on the brake discs / pads - with the wheel removed this is a safe option, wheel dry, back on and so on etc... I painted the steering track rods and the hub sections (that rust) - with hammerite smooth paint as well as the brake calipers and the outer edge of the discs; nice shiny flame red matches the car colour. Whilst so doing - the alloy wheels each got a spray; result little debris build up and nice red brakes, no rusting hubs and years of less hassle through no corrosion. It's a weekend's work mind!