There are some good videos out there, for example Part 1 - How to remove swirls, scratches and water spots using a Porter Cable 7424XP Polisher - YouTube
Ignore the fact this talks about a Porter Cable, your polisher will behave in the same way. There is a great guide from Detailing World http://www.detailingworld.co.uk/foru...apolishing.pdf
this was written quite a few years ago and so a lot of the products which are mentioned have been changed quite a lot but it is great at talking about the process and technique
If I was starting out and looking for some polishes I would get a bottle of Meguiars Ultimate Compound (Halfords etc) and a bottle of Megs 205 Meguiars #205 - Ultra Finishing Polish 8oz - Clean Your Car
(sold by nearly every online retailer). Both products will cost about £10, no need for large bottles unless you own quite a few cars and intend doing a lot of polishing. The big advantage of polishes like the Meguiars is they are very flexible i.e. you can alter the amount of cut by using different pads. Nothing wrong with the Menzerna polishes suggested above but they do work in a different way. Plenty of alternatives out there eg Scholl, Optimum, Sonus etc. All of these will do a good job.
As for pads, there is a high degree of personal preference when it comes to brands although the only one I would say not to buy is the 3M pads; my view is these are too soft for a DA although they are near perfect for a rotary. I would get at least one compound, polishing and finishing pad. My guess is the Chemical Guys Hexlogic pads are probably the most popular pads on Detailing World although there are plenty of alternatives.
If your budget allows, get some spot pads and backing plates eg Products - Serious Performance Products - Serious Performance
again lots of alternatives so don't worry who makes them. The big reason for buying spot pads is they allow you to work on intricate areas such as bumpers and door frames
Other stuff you should buy if you have not already done so. Masking tape, 3M is most popular. It is important to mask up panel edges and trim, this protects the thinner paint at the edge of a panel and any delicate trim. Get some brushes, there are dedicated pad cleaning brushes but I just use some soft toothbrushes, it is important to keep the pad clean. You will also need something to clean up after polishing, polishing oils are useful when polishing but can interfere with waxes or sealants and so need to be removed. Lots of people use IPA (5:1 dilution) and this is a cheap option which works fine but IPA does not contain any lubricants so care is required when wiping the IPA away to reduce any paint marring. There are lots of commercial products such as CarPro Eraser but many firms do alternative products eg Bilt Hamber. For a finishing polish I use Optimum polishes which have the advantage of they can be simply cleaned away with a damp cloth although the Megs 205 I suggested at the start is probably the benchmark product
It is common for people who are new to polishing to complain about lack of progress, be warned, polishing is not a quick process, it can easily take a day (or longer), the other common mistake is to move from working in a small area eg 18" square to a much larger area, all this does is reduce the effectiveness of the process and increase frustration with the result it all takes much longer.
Hope this helps