I'm doing the exact same thing when I (eventually) tube up and just grabbed this controller off the MM.
The controller comes with 2 input cables: one that is a simple 4-pin extension for connecting to the motherboard, the other is a split input with a motherboard connector without the 12V wire and a separate SATA connector to power direct from the PSU so you can drive lots of fans or high power fans that would normally overload the fan header.
You'll need to use this split input if you're going to control the DDC for bleeding because the controller itself, obviously, needs to be powered. So if your DDC pump has separate Molex/SATA for power and PWM cable, obviously hook the DDC into the PSU. If your DDC only has the single 4-pin cable, the PSU power coming into the controller will be plenty to drive the pump as well.
Note however this fan controller is a PWM generator, it's not a variable resistor. So if your DDC is actually voltage controlled, the fan controller will not work as it's always outputting unmodified 12V power.