First question, why are you going to machine polish it? Does it have swirls and scratches?
It's too bad that you posted this today, and your job is today. Looks like after three bumps, I'm the first to answer which plausibly means you're off to do your friends Audi w/out getting to read my reply. Hopefully all goes well...
There are a few things to know about clear-bra:
1.) Who is the manufacturer and what are their recommendations? There are typically three types of clear bra,
- Expel
- Suntek Ultra
- 3m
2.) Some clear bra's such as Suntek Ultra and Expel have "self-healing" properties. This means there is some kind of proprietary SiO2 coating that when scratched, and put under heat (i.e. sun light) the scratches disappear. If you machine polish this, you will be removing the proprietary coating, so you better be prepared to re-coat the clear-bra. One way to test if it has a coating is rinse it with a hose, if it has beading / sheeting properties similar to paint that has an SiO2 coating, then odds are the clear bra has a coating.
2a.) If the clear is fading, or hazy, most clear companies offer a 10 Year warranty. Again, focus where your efforts may best be served.
3.) Diminished returns on clear-bra: You can machine polish clear-bra, however, it is not paint. It isn't like you are leveling clear-coat to eliminate scratches. Odds are if it's heavily swirled and scratched, polish will have no effect at all... thus diminished returns for your time and effort.
I just did an Audi R8 fully wrapped in Clear Bra. There were no scratches or swirls except for the rear deck, luckily it didn't have clear bra on the area we needed to polish.
https://www.autogeekonline.net/forum/show-n-shine/115281-lsn-autodetailing-2013-audi-r8-v10.html
If you are determined to machine polish, then there is always do a test spot... Again know that there are diminished returns with clear bra AND, if you are trying to get swirls and scratches out, you may up causing too much heat build-up depending upon speed, pad and product. The test spot will reveal if your efforts will be needed or not.
IMO, I stay away from polishing CB, it's just not worth the time or the risk. Even on my own vehicles. Just to give it some TLC, do a good detailing job and top it with ReLoad.
