I like farecla stuff, though I didn’t realise there’s so many G3 products so I’m not totally sure what the older stuff I have is- I think it’s the ultra abrasive, it’s very full on but good if you don’t want to piss about with 10 different products, it can go all the way from wet-and-dry to nearly-finished. I like how it naturally breaks down as you work so starts very abrasive then softens, though that’s easy to screw up.
I don’t know if they still do it but halfords used to sell a rubbing compound in an aerosol, it was piss-weak, but actually pretty damn good at finishing- more a polish than a compound in all honesty but I got good results with it
(this is all finishing new paint rather than repolishing, I cannot be arsed with that. I use Mr Sheen covered with a protective mud layer)