I just did a really quick vid to show that flame polishing it not that hard or scary.
I am in no way experienced, but thought i'd try with a small butane soldering iron, with the torch attachment - this way the flame is small and it heats a smaller area, and also allows you to get into the corners.
To do this really well, you would get in and spend a heap of time with 1500 or 2000 wet and dry to get all the ball trails out. I wasn't that concerned as i was mainly mucking around with subway ramps. The difference is amazing - you can see on the 1st couple its almost like painting with a brush - the plastic just goes all smooth and glossy almost instantly.
The part on the whitewater was really just a quick demo - as i mentioned on the vid, to do it properly you would take the ramp off and do both sides.
I also did the gumball machine on twilight zone and it took some quite deep scratches out.
I have made a few bubbles in one or two places, but normally its easy enough to notice when this is about to happen - the gloss seems to start to get dull - when this happens, move the flame in a hurry! Once these bubble are present, i understand you need to sand them right back, but this may not be possible.
Anyway, just wanted to put it out there to encourage others to have a go as its good fun with instant results.