My dad makes his own cottage cheese and uses that. Yogurt, German "quark", anything that's dairy and sour is good.
I use kefir/kombucha hybrid.
I tap the blender's "wimpy" button a few times to get the stuff spinning before I hit the "maelstrom" button. That keeps it from gulping too much air or scattering seeds where they won't get blended.
Blend the hell out of it. If you didn't pre-grind the seeds in the coffee grinder it takes a lot longer. My dad uses a "stick blender" also known as an "immersion blender".
Don't let your concoction get hot.
If you don't have a blender just take a mouthfull of both ingredients and chew them thoroughly before swallowing.