Once a good rubbing-out has taken place, it's time to load the pipe. With looser cuts of tobacco, such as the much more common ribbon cuts, there is an old adage that one should pack tobacco into the pipe bowl three times: "Once with the strength of a toddler, once with the strength of a boy, and once with the strength of a man." The idea is to have a looser pack the farther down the bowl one smokes, which allows for periodic tamping without creating too dense a mass for air to move through. Rubbed out flakes, however, are stronger and more difficult to pack, so a slightly different approach is needed.
I have found it to be much better to try a two-phase approach with rubbed-out flakes. I start by taking the loosest rubbed parts and lightly rolling them into a cylinder, which I shove into the bowl. I then take a pinch of a slightly coarser rub and squeeze it gently into a plug that I shove onto the top of this mass. Remember, though, that air will still need to move through all of this tobacco, so don't press everything together too hard. This can be a tricky step to master in the beginning.
The best thing to practice, perhaps, is the rubbing step. It is at first difficult to know exactly how much a given blend can take, so experimentation is key. Try a gentle rub first, then a more vigorous one, and by all means, do not be afraid to rub out a good number of flakes and set them aside for some drying before smoking. Flakes seem to retain moisture better than the looser cuts, and can prove to be an unfortunately wet smoke for a good number of days after their tin is first opened. I like to keep a good quantity of already rubbed-out flake in my tobacco pouch for later smoking.
Flake tobacco can also come in a disc or coin cut. In this form, pressed sheets of tobacco are rolled together into long logs and then thinly sliced into discs. These flakes tend to be much easier to rub out and their interesting shape adds an interesting novelty.
Beginners interested in some mild flakes to try out would be wise to look for Best Brown Flake and Rum Flake from Gawith, Hoggarth, & Co. The latter is a mild aromatic, and the former a pleasant Virginia/burley blend. Some stronger, latakia-heavy blends include Samuel Gawith's Navy Flake and Balkan Flake. For some interesting coin-cut flakes, try Escudo Navy De Luxe from A&C Peterson, or Peter Stokkeby's Luxury Bullseye Flake. These fine tobaccos should all be available online from SmokingPipes.com.