Another possibility is a small paint roller -- the ones that are about 2 cm or so in diameter and about 15 cm long. They would be non-abrasive to the paper. I suppose one could use the full sized ones, but they would absorb a lot of the chemistry. Another possibility would be those paint pads -- rectangular with the fuzz.
One could practice on smaller sheets of paper (or even full size) using just water and seeing how much liquid is needed and how to get an even coating...or put food coloring in the water for a better visual clue, but the sheets of paper would not be able to be used for the real thing.
80 pounds for a liter of Cyanotype II!! Ouch! I just worked out how much it costs us to make up 2 liters of the Classic cyanotype formula .. about US$25 (with tax and shipping)...less if the two chemicals are bought in larger amounts.