I am not a bromoilist, though I've done a lot of printmaking... take anything I say with appropriate caution.
In etching, ink is made stiffer with French chalk (talc), but sparingly. The tack of the ink is not necessarily the same as the hardnes or softness. This site sells ink conditioners, but the text on their talc page made no sense to me. Perhaps it will to a bromoil printer.