Essentially HP is saponifying first and then molding, whereas CP is molding first and then saponifying.
There is no real difference in the recipe if you're talking about most types of soap (not counting Songwind's shave soaps). The main difference is that you might want to use slightly more liquid in your HP so the soap is easier to stir and to put into the mold. I use a lye concentration of 25% to give a little more liquid.
One tweak you can do with HP is to add the superfat after the cook is over to ensure a particular fat is the superfat. You don't have to do this -- it's just an option. Another is that you may be able to use less fragrance with HP, since fragrance is added after the cook so it won't vaporize as much. There is no difference in the cure time, however, regardless of what people say.
So to answer your question, yes, you can HP any CP recipe and you can use a slow cooker to do it. Just use a little more liquid. Some people also put plastic food wrap over the cooker rather than just the lid to really reduce evaporation.