I thought the soaking was a health thing, not just a cooking thing. Isn't that why you discard the soaking water and replace it with seasoned water?
My crock pot says specifically not to use the low setting to cook lentils (only says because of 'toxins')
I rinse the lentils/beans first in a big plastic jug, then add hot water from the kettle, pop the whole thing in the microwave until it is properly boiling, then leave for (at least half an hour but often until I remember), heat up again, and then drain and rinse.
The soup plan sounds great; I would consider adding some chilli and a teeny splash of vodka.