Alcohol should only be used to thin acrylics. Water works with acrylics, too. I've also read many times that Windex (glass cleaner) can be used to thin acrylics, and to clean brushes that were use to brush acrylics (never tried Windex myself).
Enamels should only be thinned with thinners made for enamels. Personally, I use thinner made by the paint's manufacturer to thin the paints for use, and then I use paint cleaner/stripper (not thinner) that I buy in bulk at Lowe's or Home Depot to clean my airbrush and paint brushes. Don't thin your paints with the paint cleaner - it will probably produce results that you don't want.
Not sure where you can buy paint cleaner/stripper in Italy. Most home repair stores should carry it. You should be able to buy paint thinner wherever you buy your modeling paints.
Devil Dawg
On The Bench: Tamiya 1/32nd Mitsubishi A6M5 Model 52 Zeke For Japanese Group Build
Build one at a time? Hah! That'll be the day!!