you have many options, but if you don’t have your own mailing list built up already, my suggestion is to hook up with some arts organization of some sort. In mount rainier, you could try talking to joes movement emporium, brentwood arts center, or the directors of the washington glass school, flux studios, or red dirt studios about teaching workshops there. Mountpelier Arts Center or Greenbelt could be good options too.
in DC, might be an option to talk with Capitol Hill Arts Workshop, Artspace in Shaw, Art Enables in Woodridge, or Pleasant Plains Workshop.
Anyway, thats a handful of places to think about. good luck.