Can't you just get a pen, paper a lighter and CLEAN needle or edge for the SMALL blood sacrifice and go to the woods or somewhere you know is safe and would have privacy, the astral temple technique works but this is an important thing, if you can do it physically that would be ideal.
You can write out the dedication at home, fold the paper into a breast pocket or even your shoe if necessary and just perform the dedication away from prying eyes, it takes like 5 minutes the hardest part is the cut and it only needs to be a drop or two.
The astral temple technique basically involves entering a trance and then visualizing the whole thing in an "astral temple", essentially just visualize it.