There are a whole variety of conductive paints available, mostly over the internet. Metallic markers and paints that you can get from craft stores are typically NOT conductive. Conductive paints are not cheap, but they are affordable and can be used in many of the processes described in the recipes on this website.
Copper paint from LessMF:
Make our own conductive paints, glues
Tend to be very highly conductive. I prefer water based because they tend to dry/cure at room temperature and are easy to mix with acrylic bases and thin with water. Solvent based versions often have to be dry/cured at high temperatures for long periods of time and are messy to work with.
Silver paint is contained in conductive pens that are sold for fixing electrical connections on circuits. I have had little luck getting these pens to work well and dispense their conductive ink nice and smoothly. But you can easily cut them open and extract the
Google “conductive pen” and you should find lots of results.
Extracting paint from a conductive pen:
WB-101 water based silver paint >> http://www.conductivecompounds.com/WB_101_Water_Based_Silver_Conductive_Ink.html
Midas silver paint (solvent based) >> http://www.riogrande.com/MemberArea/ProductPage.aspx?assetname=335068&page=GRID&category|category_root|118=Finishing+Equipment+and+Supplies&category|cat_118|282=Electroforming&t=lp0
M.E. Taylor Engineering
SE-101 silver conductive paint >> http://www.semicro.org/silverpaint-18silver15g.aspx
Cu-Pro Cote is a water based copper paint >> http://lessemf.com/paint.html
Tend to have high resistance, but cheap and easy to work with.
Y-Shield is a water based carbon paint >> http://lessemf.com/paint.html
Antistat 268 is a water based carbon paint >> http://www.conductivecompounds.com/ANTISTAT268_Conductive_Coatings.html