Most peoplpe inject sub-q for localized fat loss. Kefei's have been known to give some people red welts. For most, they go away after a week or two (the case w/ me), for some they don't and injecting IM solved the problem. As for maximum efficiency, some will tell you PWO, some at night, some in the AM.
Personally, I do 2 i.u. in the am and 2 i.u. PWO.
Hope that helps.