Well from my studies it is also called camphor weed...SMELL it! but different spp.. Heterotheca subaxilaris, latifolia or scabra
otherwise known as telegraph plant, false arnica, mexican arnica
Michael Moore mentions grandiflora under this entry so i'm assuming it cn be used in a similar fashion.
he also says a tea or diluted linament is antiseptica nd anti fungal, when you need to wash a wound, scrape or cut prior to bandaging. also the salve or linament is an excellent rub for sprains, dislocation or hyperextensions. Doesn't work as well for arthritis as true arnica, but does work. best used when there is pain upon movement.
in my studies this was definately an external use only plant, and i collected some leaf this summer from the rosette stage, but traditional mexican use calls for the flowers. Both will work...use the whole plant in fact!!