Buy a high quality charcoal (like Kingsford charcoal); the cheap stuff does not burn predictably.
Fill one charcoal lighter can with charcoal for each Dutch oven and place on fire grate above a roaring fire. For each 3 to 5 cans, light one additional can. When most of the briquettes show some light gray color, the charcoal is ready to be used. For 5 Dutch ovens, prepare 6 charcoal cans.
To eliminate the need for lighter fluid, there are various other methods of starting charcoal.
One method that can take 1/3 the time involves using charcoal starter made from a five gallon can with a hole cut out of the side and a wire grate placed in the center of the can. A charcoal chimney can be purchased from your local Dutch oven dealer or Bar-B-Que dealer.