One way to get info on any demon you are considering as an 'injection' for a meatsuit is to look up if they have any specific enemies that can match or beat them into submission. There are angels from the Kabbalah and Shem ha-Mephorash that have battled and beaten certain demons, so as these angels have either planetary or astrological attributes then it is quite reasonable to assume that the demon may be ruled by such planets and zodiac signs or else these attributes can help in binding them. But we are dealing with Malkuth/Lilith in Assiah, in other words this earth that we reside on. If we are to 'ground' a demon in a human body we can no longer allow it to be bound by planetary or astrological limitations or else all we will be doing is having a meatsuit being shared between a demon soul and an atheist 'soul'. I think such a situation could or would describe things that are commonly called mental illness such as schizophrenia, split personality, etc.

So injecting a demon soul would require a complete takeover in spirit, body and soul. So the issue of a sigil which is best drawn on a planetary magic square would have to be done on the planetary magic square (kamea) of Earth.

[I'll just add this here, for some reason most occult books that deal with kameas either cannot or will not do a kamea for Earth. I dont know why, the only time Ive seen a kamea for Earth in a book was in a book on thelema which I think was to do with Crowleys teaching.]

If a demon could be bound by such a kamea and indeed prayed once for every planetary hour and did this every day, the ability to hold the body should be stable. Also it would not be limited by the planetary hour or day it was before, as for the zodiac sign? Dunno....arent we all bound by the zodiac to some degree? But it also depends if the demon willingly wishes to retain the body.