DIESELis very good ,agitate with soft cloth this will save the bother of waiting, wash off with warm soapy water, not forgetting that diesel is a lubricantDeisel is very good, just wipe it on and leave it to disolve the black specs.
I use car polish with a little light tcut for the difficult bits. It is laquer paint after all (what would you use on your bonnet?) . Then once clean and shiny, blather on some alloy wheel wax to seal and protect it. (got mine from Halfords so its easily available) Re-apply every 4-6 months or so and the dust just wipes off.
Try "Wonder Wheels", amazing stuff, I use it on both my cars and bikes, Halfords sell it.