for a finishing polish on holden paint (which is on the sticky side) I like meguiars M205 from their pro range or Scholl S30 (the only scholl product I like). Neither are the best for all jobs, but are easy to work with on holden clears. You might even be able to one step it with some Megs D300 if you can get it (I buy it from the UK but there is one supplier here for it apparently) or Meg's ultimate compound (which you can get anywhere - autobarn/supercheap/etc). Ultimate compound is a handy tool, if a bit oily and dusty, for sticky paints. It's not what I reach for when working on euros and hard clears but for the sticky jap paints (holden included) it can come in handy. It has a moderate cut but finishes relatively well if using a DA polisher (not the rockwell rotary you have though) and polishing foam or finishing microfibre pads.
I'd suggest picking up a half decent DA if you want to tackle it yourself. That rockwell rotary is going to throw a heap of heat into the panel and make working it more difficult, as well as binding up and wanting to walk away on you with the sticky paint. Rockwell have a DA for about 80 bucks I think that is apparently not too bad if you can find one with a straight spindle so the backing plate spins true (big time fault). It's apparently noisy as hell and not the smoothest thing, but does have an 8mm orbit and will take good pads, rather than the tie on wool/microfibre junk.
Above that, look at the new concours dual force from
www.waxit.com.au - with an 8mm orbit (on sale for about $200 at the moment, I think), or the zentool from
www.zas.com.au with a 21mm orbit (about $300). I would say the concours would be the better beginner tool but if you know your way around a polisher the 21mm Zentool will give quicker results. If you were going to use it every day, I'd say go for a Rupes 21, but $700 for a tool you'll only use occasionally is a bit over the top, whereas I'm using mine just about every day. The concours will do everything you need it to and be much more forgiving and safer than a rotary, particularly a rotary without electronic torque control (most lower end rotaries).
Without seeing it, there's no way I can tell you what's going to be the best option to fix it. Sometimes a waterspot remover will shift it if it's just on the surface - most use Acetic acid (try some vinegar - same same), sometimes a stronger phosphoric acid or hydrofluoric acid will shift it, but if it's etched, meaning it's pitted into the clear, it will at the very least need a moderate compound if not more.
If all that sounds too daunting, I have a pro contact up that way that can probably help you out unless you have a reason to come to sydney and I'll take a look at it.