How to clean lecithin residue?
This is one of the reasons I hate working with liquid lecithin - it's the most viscous and sticky substance I've ever had in my kitchen (or, frankly, anywhere).

Prevention seems to be the best approach; try not to let the lecithin directly touch any utensils or cooking surface. Grease up your spoons, preferably with something reasonably solid at room temperature like coconut oil, butter, or margarine. That makes the lecithin slide off more easily, and you only need to clean off the grease afterward (i.e. with soap).

The only way I've been able to clean surfaces or utensils coated with the lecithin itself is lots and lots and lots of warm water and paper towels. Warm water is important since lecithin does not dissolve very well in cold water.

Good luck - personally, on the infrequent occasion that I need lecithin these days, I just stick to the granules.