I'm not exactly sure what advice/info you are looking for. But an
easy way to do a mold of the finger is with "body-double" a product
by smooth-on amazing stuff. I made molds of my ears, but as a test
run I did a mold of my finger (much easier than the ear i might add).
There is a fast set that is ready to de-mold in five minutes.
the company's website is http://www.smooth-on.com In addition to
the mold making materials, they have a variety of things to make
positives. I made a bunch of plastic fingers which are actually
really fun to display rings on, kind of weird, and creepy b/c they
are so realistic, but lots of fun. I even painted the fingernail!
anyway, the usual disclaimer, no i don't work for them, have stock
in their company or anything like that. The products are wonderful
and the people are really helpful if you need to call and talk to
them. sounds like a great idea to get a good fit!