I use nearly boiling water and just soak the seeds usually, without nicking them, in darkness and let the water cool, the seeds imbibe (absorb water and swell) fairly quickly which can be easily observed. An hour or two is usually good, but I tend to leave them overnight.
I then plant the seeds in a potting mix in containers, usually under lights indoors.
I used to nick them all, but experimented with hot (near boiling) water and now use that in most cases, because it works well for me. I didn't know of anyone else using this for Ipomoea when I tried it, though it is a common method for Acacia.
