When do I actually need a heavy cut compound rather than a lighter polish?

Heavy cut compounds are for significant paint defects: deep swirl marks, scratches from poor washing technique, and sanding marks from wet sanding or orange-peel removal. If a medium polish and a test spot on the bonnet fail to remove the defect after a full set of passes, step up to a heavy compound. On paint that only has fine haze or light swirls, a medium or one-step polish is the right starting point.

Does a heavy compound always need a separate refinement pass afterwards?

Yes, in almost every case. A heavy compound such as Koch Chemie H9.02 cuts well but leaves its own visible marks without a follow-up refinement step. After compounding, a finishing polish such as Koch Chemie M3 or Scholl Concepts S40 on a soft foam pad removes the compound marks and brings the paint to its gloss ceiling. Skipping the refinement pass leaves a dull, scratchy finish even though the original defect is gone.

What pad type should I pair with a heavy cut compound?

For the first compounding step after wet sanding, a wool pad on a DA cuts sanding marks faster than a foam cutting pad and builds less heat because it removes them in less time. A Rupes medium wool pad with Koch Chemie H9.02 works well for that first set. Switch to foam pads with a finishing polish for the refinement steps. Avoid starting a heavy cut with a soft foam pad as it will not deliver enough aggressiveness to remove deep defects efficiently.

How do I avoid burning through clear coat when using a heavy compound?

Check paint thickness with a depth gauge before any correction session and stop if readings are consistently below 80 to 100 microns. Always do a test spot on a 2 ft by 2 ft section of the bonnet before committing to a full car. Work in a garage or shaded area, never in direct sunlight, as heat causes polish oils to flash off and the pad to drag rather than cut. A DA polisher is the safer format as it stalls rather than burning paint if you apply too much pressure.

Can I remove an old ceramic coating with a heavy compound before re-coating?

Yes. A ceramic coating cannot be stripped by stripping shampoos or heavy-duty degreasers alone. Machine polishing is the only reliable method, and even a light DA compound pass removes the coating layer. A heavy compound on a cutting pad makes the removal faster on thicker or more durable coatings. Once the coating is removed, follow with a refinement pass and panel prep spray before applying the new ceramic.