Try moving the pick faster and be less gentle.
Most people only do not apply enogh force on raking to lift the pins up to the shear line. Do not forget that the force you apply is distributed along many pins. Moving faster gives the force in shocks, like a pick gun, so prevents overlifting the pins already set while easily lifting the others.
By the way, I figured out that hook is the best pick for raking if you use the proper method (insert to hook as deep as you can, and pull it out fastly) and if you do not have spool pins (bouncing the tension tool is not possible in that single motion).
Here is the easiest method for the spool pins that I figured out myself:
A spring loaded tension tool is required. After raking a few times the keyway will turn slightly, fallsely setting one of the spools. At this point you need to find the falsely set spool pin (the most solid one), push it farther strongly against the spring until the keyway turns back to the normal position and the pin is properly set. But do not do this if your pick is made of a mild steel or it will deform in shape after long use, due to the strength you apply. Any way if you can make your picks, it will not matter. Easy to make hooks!
You can do the same thing with a standard tension tool, but you need to release the tension mostly at the point of re-setting so you will lose already correctly set pins. It seems to be theoretically possible, but I could never manage since all my pick-resistant locks have more than one spool pins.
But do not forget that raking with a hook is quite aggresive and damages the pins if you do it for a long time (especially with a pick that is not sanded properly).
As a general rule: If you can rake most locks in seconds, and a specific lock gives you trouble, it is due to a pin required to set deeply. Try raking with a deeper hook or find the single pin that do not set, and push it alone. Contrary to raking, a bit forward and downward force helps in these deep set pins. And I always make a small inward slope at the tip of my deep hooks that are difficult to insert. It helps a lot. See the following link for an example:
http://www.lockpickshop.com/p-SLS-11.html
Regards...