Not sure what the brakes look like on an 806, but I've always cleaned oily brake linings by setting them on fire with a torch. (off the tractor of course).
Might sound extreme, but it works. You don't have to worry about them getting too hot - they're made for high heat.
It draws a lot more of the oil out than simply cleaning them with a solvent.
Then finish with brake cleaner once they're cooled off. (don't get brake cleaner hot - it can kill you, or at least the old stuff could)
Of course your bigger problem is putting new seals in to stop the oil.