More after the jump.
I accomplished this feat— painting with light— with 8 sparklers and my trusty DSLR. I used my tripod because I wanted to minimize movement to try and get really clear photos. This was almost impossible, but I want to try it again, tweaking my settings to try and achieve super clear pictures. 
Technical Stuff:
f-stop: 22
shutter speed: 13 sec/15 sec
ISO: auto (I need to read more about the right ISO settings for this…)