For S40
You can use pressures ranging from absolute zero, to maximum with a free-rotation 8mm DA when using Scholl, and need to depending on the stage of the set and that required by the defects at hand. So too, can the travel speed change within a spectrum.
When spreading the polish for the initial pass, I would suggest using the weight of the machine alone. After this is accomplished, you can bump-up speed, and apply as much pressure as is needed. If you want to adjust the aggression of your pad/polish combo downwards, you can continue using the weight of the machine. If you want to truly maximize it, though, apply as much pressure as the machine can handle while still maintaining 1-2 RPM's per second of the backing plate. One can also use anything in between; how much pressure to use exactly requires some practice. If you're using less pressure than maximum, you might also want to increase your passes by 1-2 over what I listed, as the reduced friction will cause the product to break down just a little slower.
For the final pass at speed one, I'd recommend machine weight, or one machine weight pass, followed by one at absolute zero... Whereby one lifts the machine to take its weight off of the pad, and lets it free-spin, while still keeping it level with the paint. This takes practice, but can help in finishing down on very sensitive paints/plastics.
As for travel speed, again, this depends. Generally, the approximately 1-inch per second arm speed rule of thumb applies very nicely on 8mm free-throw DA's, in regards to Scholl. However, on more heat sensitive surfaces this can be increased to 2+ inches per second, and on harder paints, you can shrink your polishing area from the standard 18X18 inch zone with a 5.5" pad, to 12X12, prime the pad more heavily, and polish at even less than 1-inch per second for greater correction.
There are always lots of ways to adjust your technique to change your results to fit the application... Furthermore, all of the Scholl polishes themselves are a little different. All of them hold onto their primary abrasive size for different levels of time before diminishing. All of them have a different 'sweet spot' when it's best to stop polishing. Depending on the tool/pad you're using, the nature of the paint, and your pressure/speed, the number of passes you take and your arm travel speeds change. This sounds complicated to try to figure out in the field, but it really isn't...
Scholl polishes/compounds will tell you what to do, and when you need to do it. You can feel the transition point when the abrasives have started to break apart, and moments later are fully broken down... You feel the point when the polish loses friction, and goes smooth under the pad. This is more obvious with the more aggressive products (It's easier to feel with S17+ rather than S40.), but even on the mildest ones can be detected... You won't see it, because the lube will look the same. You'll feel it... It's not a feeling that will smack you in the face (It's more noticeable with some pads/machines than others... It's real easy to feel on rotaries, with the compounds. Less so on a forced rotation DA, with the finishing polishes.), so you have to let your mind/hands relax to sense it, and stay focused, but it's always there... Once you feel that transition, lighten up, and just ride out that finishing cycle... How long you ride the finishing cycle depends on various factors. There's a 'sweet spot' of when to stop. Figuring out that 'sweet spot' is more about practice than any feedback you'll get. You get a feel for the timing... How long is 'too long', when the swarf starts to do more harm, than running the finishing leg out can keep doing good.
Another note... My technique with Scholl was developed mainly on very soft, very sticky paint, that was very unforgiving. These paints require exacting timing and pressure control... Medium or harder paints are much more forgiving, and you won't see the differences in finish quality by running the polishes a pass or two too long or too short, that you will on soft finishes. If your paints aren't that problematic, realize you have some wiggle room... Play by the numbers if you can't play by feel... You're not going to get spanked for it like you will on the soft stuff. On 'normal' spectrum paints, you can just get the basic concept of how these products break down, and relax to a certain degree. It's when you're in an extreme situation that you have to maximize every ounce of what these polishes can achieve, that you need to get REALLY HARDCORE about having your timing/pressure transitions being perfect. Otherwise, you've got some margin of error to play with.
