Recently my old Macbook died. So right now I am using an old PC, running a Linux distribution, Ubuntu Studio. This is a free operating system that comes bundled with graphics, audio and video programs, also free.
I found there was a steep learning curve on the installation, but I have it running just like I want it now.
One of the graphic programs is GIMP. Similar to, but not as polished as Photoshop.
Here is a cartoony oxydized red Studebaker Lark. It started out as a rough pencil sketch, scanned, inked and colored with GIMP. I also want to mention that I use a Bamboo digital pad which works fine with my Linux laptop.
One of my first cars was a 1960 Studebaker Lark.