I use both a wheel and the Dual Shock 3. Depends on if I have the time to get out the cockpit and set up my DFGT.
When I am drifting with the Dual Shock 3 (same as Sixaxxis), I use the analog sticks. I have been drifting since GT1, and have been drifting on GTplanet (posting videos, entering competitions, hosting competitions (i.e. Official Gran Turismo Drift Competitions) since GT3. I've always used the analog sticks, as they give you far more control and variability than the buttons could possibly provide. I've tried using the triggers ala Xbox 3crappy (umm, I mean 360

), and I just don't feel comfortable with it. I have always used the L2 R2 buttons for shifting, which means I would have to reassign them to different buttons. Maybe I've just been using the sticks for so long, but I seem to have a lot more control with them.
As for how to drift with the controller. Watch videos on Youtube, read threads on drift techniques (i.e initiation techniques). Finally, learn what different forces acting on your vehicle will result in (i.e how braking effects the movement of the car in different circumstances, weight transfer, throttle on/throttle off effects, etc...). There are no shortcuts. Many of us that seem to drift well in the game, have been drifting in the GT series for years, and/or drift in the real world (like myself). All the real world techniques apply to drifting in the GT series. All you have to remember is to be precise with your inputs. Learn to make small adjustments with the analog sticks (or triggers) I would say stay away from using the D-Pad. Unless you have super human control over the amount of pressure applied to the buttons (like GTP's own Sheron), you're just not going to be able to make small enough adjustments, and your front wheels are going to be twitching like crazy (see most all drift mode videos to see examples of this).
Lastly..... Practice, practice, practice. Nothing can substitute for seat time.
