The reason I rented the throater was because mine had a shallow throat and I couldn't seat the 405 grain Remington jacketed bullet on the cannelure without digging into the lands.
It shot great though even setting my COL a little deeper, and not seating on the cannelure, but I still wanted to be able to reach the factory COL for that bullet without a problem.
I took an empty piece of brass and using a dremmel I cut a slit about a half inch long lengthwise on the side of the casing, which allowed me to insert a bullet and line it up at the cannelure. I then placed the dummy cartridge into the chamber and closed the action, and when the bullet touched the lands it pushed the bullet back into the case, which I then measured to see how far it pushed back, and and then I just added about another .002 to that measurement which gave me the depth that I needed to stop at.
Take it slow and measure as you go. I could have gone a lot deeper and probably wouldn't have made any difference, but I didn't want a long jump to the lands, and I'm not going to be using any bigger bullets than the 405 grain Remingtons.
That's the way I did it, and hopefully someone will come along and tell you the proper way to do it though! Good luck!