Glenn: I am using 100% epoxy material to fill vias 100%. This material is not conductive but does a good job. You can use screen printing method (pushing through the via holes). For conductive material, you can use either silver, copper or a combination in paste form using the same method. I did not use this method but the manufacturer claims: either paste can fill vias 100%. If you want the manufacturer and/or a contact person, write me an e-mail. Hope this helps. Dejen Eshete Santa Clara