Doing a fur transfer or hand laying the hairs like one would do for a crepe hair beard would both work. Hand laying the hair works like applying roof shingles. Start at the bottom and work your way up so the new layer covers the old. You can change the hair direction as you go to match natural hair patterns.
This lesson covers hand laying a fake bard, with a lot of great tips.
I don't believe any of the mold making in the current lesson lineup uses syntactic dough. But with the prevalence of syntactic dough and epoxy molds I'm sure a lesson covering these materials is not far off.
For the epoxy coating, brushing on multiple thinner passes may help a bit with the material not settling the way you want. There is also a product by Smooth-On called "XTC-3D" which is designed for coating 3D prints, but it too is a low viscosity self-leveling epoxy. It may also not be in your budget, since I know their products are a bit more expensive some times.
For lighting the runes there are a few things you can do to get better results. One is to mask off the runs and paint the armor first, then mask of the armor and lightly mist the clear runes. After that you can remove the masking and lightly mist again to blend things. The idea is to not fully cover the runes with paint, but to coat them in with more of a fog of tiny dots.
When the runes are covered from the back (with no ambient light able to shine through) they should be less visible. And when lit by bright LEDs they should stand out.
You're headed in the right direction with your testing, just keep at it!