I bought a set of 2" and 5" polishing pads but need to get some compound for it. I assume I sand it first with 2000 paper. Bottles of compound seem to start at £15 each.
3m range is one of the best on the market.
1500/2000/3000 (possibly 5000) trisact discs
Green top fast cut plus,
Then yellow top,
Then either white, light blue, dark blue dependant on colour and finish required.
I buy the big bottles but they are £35 a pop now. But will last for ages.
If you want something easily available, I had really good results with a da polisher and Meguiers Ultimate Compound, then Poor Boys Black Hole Glaze (for dark cars) on top. You need to clay mitt first to get the paint smooth. A litre is a lot of compound, especially if you're not doing the whole car. It's more about taking your time and technique than about the amount of compound. Lots of good advice on the Detailing World forums.
I use a Makita 9” polisher with Menzerna pads and polishes. This can be bought in 250ml bottles, lasts ages and gives the best results I’ve found in 20 years of doing it.