I've gotten a decent etch in less than 8 hours. With sand, though because (I went for easy, and didn't want to wait to order the silicon carbide). not sure I agree with the "smart" assessment...
Also, with a new barrel, sometimes it needs to sort of get cleaned out before the silver comes out really shiny. You'll want to rinse the barrel several times, and possibly run it for a while with the soap and shot to get it all nice and cleaned out.