Draft the layout on a PC
Hang the fabric in a conference room at work in front of the whiteboard.
Put the layout on the conference room projector
Trace the projection onto the fabric using chalk
Roll up the fabric, take it home, unroll, and paint.
I did this once. I used a black bed sheet and white fabric paint as stated above. I made a grid on the drawing and a grid on the sheet with chalk. I drew the banner at first with the chalk, then traced it with the paint when I was happy with it. Once the paint was dry I washed and dried it to get rid of the chalk grid.
We got our 8'x8' banner from an ebay seller for $63...6 years ago. Whomever does it for you, find out if it will be delivered rolled up or folded. If folded, you'll need to let it hang for a while to get the creases out.
I know a guy.. who emailed their band name and logo to some place in Vietnam.. and it came back perfectly in a week. It only cost $25!
It was on a big white fabric sheet... I was amazed. I don't think you can even buy a sheet that big here for $25.