I was taught to properly prepare my pieces before welding by grinding out or beveling the iron before welding. The weld will replace the medal I ground out.  Yes, 6013 can penetrate on a non ground but joint if you just turn up the amps. 

I was taught that the first weld is the one that counts and does the work of holding the pieces together.  Anything after that or on top is just for show and a waste of rod, time, ect.