If you try to use one pad for the entire work, you will be cleaning it a lot plus over time it will just not be as effective as a clean one. It can be done but you will not likely get optimum results.
If the truck has never been detailed before or a very long time, you may also just be getting the crud on the paint in the pad as well (pad will get dirty very quickly). You could preclean the paint using a paint cleaner to prep the paint to reduce this but then that is another step.
If did not want to order online, you can find a local PBE (paint / body shop) place locally that sells buffing pads. They will usually carry at least the Meg's pads.
If you are doing to invest the time, do it right and order a few pads for best results plus the orange pad may not give you the best results if that is what you finish with.