Only thing I can say is how I started, I started out small on ¼ printing paper, it doesn’t take as long draw them small and it help me get the feeling of how to draw them. Once I felt confident I went to full sheets of sketch paper, Doctor Whooves playing piano was my first full sheet of sketch paper. I’ve drawn cartoon style horses before I started drawing ponies, I enjoy drawing horses, so the best advice I can give you is draw a pony you want to draw. At least for me I put more passion into it when I do and I have more fun drawing them.
I use my printer, which has a built in scanner, it a Canon Pixma MG3100. I have used digital camera before but not on any of these. So I do know how to take pictures with digital camera, use to do it that way when I shared cartoon style horses I drew long time ago.