I have used all kinds of brush and rod to coat for ka;;itype, cyanotype and
platinum.
Changes in the ambient humidity make a practical and significant difference.
Here we expect a level of 60% so applying a 1% size to the paper first and
drying it quickly and then humidifying it before coating removes the need to add
wetting agent to the sensitising solutions. It also enables the use of a brush,
a nylon bound hake brush is very effective; in fact I would say for larger
prints, above 10 x 8, a brush becomes essential.
Lots of different opinions and none of them wrong.
Terry King