I initially used CQuartz UK Edition and it requires strict prep and application. It still seemed to be working and looked good 18/24 months in... with a top-up of Reload (twice). Also needs a week of aftercare if you plan to drive in the rain. I switched around 18 months ago to Gtechniq C1.5 v2 Silo Seal which provides similar protection, but is far, far easier to apply. One full prep 18 months back (mostly to remove the CQuartz) and 2/3 double applications of C1.5 per year gives a deep gloss protection. Great on the wheels too… I previously thought Poorboys Wheel Sealant was good.

I think CQuartz was tougher and gave more protection, but C1.5 seems to be more bug/tar resistant and a gives much nicer lustre... two coats last about 4/5 months.

Other stuff I like for the prep:

Auto Glym Intensive Tar Remover
Bilt Hamber Auto Clay Bar (only needs water for lube)
Meguair`s Ultimate Compound
CarPro Eraser