First, you need to max out the stock camber bolt. Rotate that bolt and you'll see the hub moving slightly in and out at the top. Find the position where the top of the hub is as far in as it will go. That has maxed out the camber bolt.
Now you do get that last bit of camber by taking up the slack in the bolts holes, kinda the way you described. The way I do it is to place a short section of 2x4 lumber under the "hat" section of the rotor and gently jack up the 2x4 until the slack is all taken up. Now I can tighten the nuts while the jack holds the hub in place. Make sure you do not rotate the camber bolt while tighten the nut.
The amount of extra camber you get might not be significant, but it only takes a second to do.