My foolproof method for finding Seamount from HITW: First go to Lone Metridium, then head due north for 130'. Try to stay up at 60'-70', because the bottom is relatively uninteresting along the way from LM to Seamount.
To get to LM from HITW, hug the rocks on your left as you go west from HITW. Go through the sand channel to the next ridgeline over, then hang a right. Follow that wall down to the end, then go around the point. LM will be at the end of the finger about 20' off the bottom.
To do Beto's Reef right, you really need to learn how to go down directly on Seamount and start your dive there. That will take some practice, as Seamount is nearly a point target when you're swimming out on the surface. Your best clue is the kelp: this time of year, the kelp going north from the bird rock pretty much ends at Seamount.
Bruce