It is necessary to lean on the Paddle, with the blades Extrado on the water, as your entering enters the curve. Clearly, the more weight you put on the Paddle, the harder you can attack.
The acceleration and radicality within that come from leaning into it may surprise at first but it is one of the keys to SUP.
This is really what makes it possible for such a large Board to be agile.
The foot position are the same as when surfing. It will be necessary that your feet have passed from the position of paddling to that of surfing. Obviously, the hollower the wave is, the closer to the inner rail you need to have your back foot.
Note that the more you lean onto the Paddle and the more it skips the water. This will cause you to slow down. On the other hand, this is rather imperceptible since you will only be leaning into it as hard as you need/want which will itself be proportional to the strength of the wave. The friction is therefore compensated by the power of the wave.
Also note that in fast and powerful waves, the Paddle has significant resistance and bounces off the water. It can even lead to slipping out of your hands or losing your balance.
In very small waves, you can dig the blade in the back of the wave so as to turn on the spot.