Not a noob but have questions on compounding/polishing

Ive been doing lots of side jobs. I have some people who have high end cars that talk to me about paint correction. Ive done about 5 or so and have been using D300. I have been pretty happy with the results. Then after i use the D300 i go over with and polishing with menzerna SF4000. I see people are talking about the meguires 105. Can some one tell me whats the best combo to use or what should i use for best results? also what are the differences? and last im looking for a good one step because i have people who dont want to pay for a full correction. I have menzerna 2500 for a one-step not sure if thats good?