It seems to me that Grin’s current logo (emblem, insignia) lends itself perfectly to be used in the practice of culture jamming (https://en.wikipedia.org/wiki/Culture_jamming). The smile is a lot like the Guy Fawkes mask or Andre The Giant on OBEY’s brand in that it gives off sense of discomfort in the viewer. It may be more likely subconsciously remembered because of this quality.
@0xb100d efforts with merchandise like stickers and stamps could help towards the effort of culture jamming. Much like the stickers for things like the Apple logo after every product purchase or Harry Potter franchises Deathly Hallows stickers, having stickers for Grin help to show support and push out the idea into a form of pop culture.
I wonder if anyone will ever do graffiti art with stencils or stamps on currency bills to put out a more mysterious promotion or signal. That could be interesting, though I’m not endorsing such behavior if illegal.