Welcome to the CYC Forum Before you even start polishing, it is vitally important that the paintwork is thoroughly clean and de-contaminated (shampoo'd, rinsed, de-tar, iron fallout removed, clayed, rinsed and dried)
Firstly, The Das6 Pro can easily handle machine polishing the Fiat paint...so great choice. The tight curved areas, it is advisable to use a smaller backing plate and pads...commonly known as 'spot' pads.
A 75mm (3") backing plate will be fine and also enable you to place pads up to 100mm on it.http://www.cleanyourcar.co.uk/polishing-accessories/dual-action-backing-plates/shinemate75mm-3-dual-action-backing-plate/prod_1248.html
As to which pads you will need, depends upon which polish and state of the paintwork. However, you can't go far wrong using the 'quality' Chemical Guys Hexlogic or 3M pads.
This brings me to the polishes. A paint with no clearcoat is easy to test for....Just get a soft microfibre cloth and put a tiny amount of polish on it, then rub it onto an area of paint which is clean. If , in your case, no yellow appears upon the cloth, then there IS a clearcoat on the car.
If yellow does appear from this test, then it has no dedicated clearcoat and will polish up beautifully.
Polishes: I suggest that you get 2 polishes...Scholl S17+ and Scholl S30+. Always start off with the softer pad and lighter cut polish (S30+) and see what results you achieve....you can always switch to the heavier cut polish and firmer pad if needed.