Apologies for not seeing your request until now. Cleaning the tips is for me a progressive process. First stage is Autofinesse citrus pre-wash (which I use as part of my washing routine) or WD40. If they don't do the trick I resort to Autosol, a chrome cleaner I used to use on my bike as a lad and which is still sold. If Autosol struggles to remove the baked on deposits, I use a nylon scourer. So far, with my A4 WD40 or the citrus pre-wash have been sufficient.
Cool, not had to move past the pre-wash at the moment, I use Gyeon Bug and Grime, but they the can has only done 400 miles so far, but will keep the other tips in mind!
My next concern is what wheel cleaner to use because of the diamond cut and titanium finish and whether to use Gtechniq C5 or Gyeon Rim to protect them.