The Tamiya Bf-109G-6 kit comes with masks inside the kit. I used them on my build but discovered a few things. The first thing that I noticed was that I needed to cut them out of the sheet. This was a pain. I would rather have my masks pre-cut. I did cut mine correctly, but it took some time.
The other thing that I noticed was that the Tamiya masks while nice just didn’t have the amount of stickiness that would allow them to hold onto the curves. They just wanted to straighten out and this allowed paint to creep under the masks.