Maybe consider making the chalking process part of the advertising. Check out chalk printer: https://hackaday.com/2014/08/29/the-chalkjet-an-ink-jet-printer-fo

Maybe consider making the chalking process part of the advertising. Check out chalk printer: https://hackaday.com/2014/08/29/the-chalkjet-an-ink-jet-printer-for-the-streets/ https://hackaday.com/2014/08/29/the-chalkjet-an-ink-jet-prin... And chalk bot: https://hackaday.com/2009/07/09/chalkbot-vs-graffitiwriter/ https://hackaday.com/2009/07/09/chalkbot-vs-graffitiwriter/ You could make one of those. Everyone love funny robots.