Having used the cornmeal method, be sure and remove the brake first. you have to fiddle with the powder charges a little to get the proper shoulder and it helps to use a little bit of lube on the shoulder.
I like the false shoulder method much better. It is much better and easier to get ignition and not have misfires plus it gives cleaner shoulders the first time and no need to do it twice. you can see both on www.6mmbr.com
under the articles section.