i've had and still own all the Harder Steenbeck brushes infinity, evolution, Al CR+ right down to an ultra. I have Iwata Revolution, eclipse and neo as well as some Chinese knock offs over the past twenty years. I use automotive lacquer thinner to clean the high end brushes and water and IPA for the ones that I cant retro fit PTFE seals in. Which is easy by the way.
Strip them down once a month and clean the seals and pop them in an ultra sonic cleaner. pop a bit of lube on which in my case is either veg glycerin or the sort of lube you get from Anne Summers water based personal type, if you know what I mean and I've never had a problem.
As for servicing an airbrush, lets face it, its a small hole with a needle and a spring. If you pull it apart with a screwdriver you wont find anything special. Your car needs servicing, your airbrush does not. Look at the exploded diagram and rip it apart, clean it and you'll be surprised how easy it is.
The chrome is still chrome even on the cheap Chinese brushes.
This hobby is full of myth smoke and mirrors and snake oil. Iwata lube is just glycerin but it cost £6 for 5ml. I just bought a L for £11. Don't be fooled. The manufacturer of cleaners etc don't have any special additives that you can't buy cheap off amazon.