Scratch the pattern into the steel first with a sheet of coarse grit sandpaper - it’ll give the chemicals a lot more surface area to work with; and it will be immediately apparent, but not glaringly so. You’ll be able to appreciate your own work, without catching the eye of onlookers.
LPT: It’s less immediately obvious, but much more permanent, if you paint with a brush and a mix of vinegar and salt, it’ll seed the rust…
Scratch the pattern into the steel first with a sheet of coarse grit sandpaper - it’ll give the chemicals a lot more surface area to work with; and it will be immediately apparent, but not glaringly so. You’ll be able to appreciate your own work, without catching the eye of onlookers.