RE: Run a brushless motor without ESC?
What you need is a "simple" bit of circuit that basically pretends to be a receiver. All you need to do is put your 4.8v on the red wire, ground on the black/brown wire, and a square wave with the right pulse width on the signal wire. Looking up the signal info isn't complicated, it's the same signal that all normal servos use.
pilotpete2 pointed out that a servo controller is exactly that kind of device with a more complicated UI than you need, since you just need to send the minimum pulse rate and the maximum rate for the extreme travel range. But you should get a cheap ESC and a cheap servo controller as pilotpete2 suggested as a starting point.
I forgot to add, you'll want to make sure you know what kind of current you're going to pull with your motor, since it sounds like you aren't using a prop. If you have a very low load, you can use a really small ESC and you might not need one with a BEC.