Something else to try, kinda like others have said is to do this:
Best baits are sandshrimp, nightcrawlers and tube worms for me. Sand worms are good too but I have never tried pile worms. They also seem to like small clams and I have seen many limpets on the stomachs of a lot of kelpies I have caught in the past.
Take about 1 ounce of pencil lead rigged as a slip sinker. More if you need to combat the waves to get down into the hole.
Put on a really short leader, I will use as short as a 3 inch leader for doing this on a size 1 hook or whatever size you like.
Find some rocks that have some spaces between them and start vertical jigging trying to find a place where the bottom drops off and goes down into a hole. Once you find it, slowly jig it up and down with a shrimp and wait for the take. Hitting right beside a rock often finds the deepest holes.
Here is the key to this technique, do NOT set the hook right away. Feel the bite and then wait for them to pull on it, then set the hook. A lot of people who try this setup lose a lot of gear because they set the hook too soon and pull everything into the rocks. And the short leader keeps the bait down with the sinker so it is fishing deep.
When it comes to Kelp Greenling, I have NEVER been skuked when I target them this way. I may catch a lot of small ones but sooner or later larger ones will come into the hole. If you find a good spot, if it works the same way down there, you can pull 5-30+ kelp greenling out of the same spot and may even hook into a couple bass and green ling. Not to mention the occasional ling cod that will latch onto a kelpie once you hook it in the same hole.
Oh and be ready to lose some hooks. I go through between 15-40 on a full day fishing this way. Is why I use a lighter line for my leader as the weight rarely snags up on me. And more often than not I can work the whole thing lose by jigging it up and down a couple times