Caig vs Kontak vs new WD-40 contact cleaner

I use Caig products.I own the red 'serious' cleanerThe Gold mild cleaner and contact enhancer.Everything get treated with the 'Gold' product. Apply and wipe off with paper towel. If you can see some left. that is too much.Just want an invisible film left.If a new item, with some tarnish, I may use the Red first.And for ordinary old copper. like used electronics AC plug ends, really tarnished up I use a car product... Meguiar's Scratch X (which I have laying about anyway as I use it for 'fixing' scratches on CDs.) The scratch X really strips the tarnish off with a little rubbing. Plus it polishes the surface. Then I use the Caig Gold.I have a bottle I have used for over ten years, along the way I spilt  a third of it! and I still have some left.I trust the Caig products 100%.