I have to avoid glycerine because it does nasty stuff to my skin. You might watch out for that if you have extremely sensitive skin in case you also have an allergy.
The absolute gentlest scrub I use is to dump half oatmeal and half cammomile buds (or even tea if I'm desperate) into a food processor and chop it a bit and use it on my face as is. If I want more serious cleaning for the bath I also add finely grated soap to the mix and then pour it into a little muslin bag for scrubbing- that way you don't have too much sitting around wet at one time. It also looks really pretty sitting in a jar waiting to be used. Hope this helps.