We have one of the Rio Midas pen platers. We use it mainly to plate our
masters before we mold them. You get a better mold surface if you plate
with palladium (cheap) or rhodium (expensive) before you mold the object.
We clamp the clamp ended wire onto the sprue, and then submerge the pen
end into the plating solution and submerge the piece into the solution
about 1/2 way up the sprue. It takes about 10-30 seconds.
Any time we need to do a two tone piece, ie: rhodium plated onto a section
of yellow gold, we mask the area we don't want plated with nail polish.
We then have a friend plate it using a regular plating rectifier and heated
rhodium solution to do a better job. The piece is submerged, and the
places masked by the polish do not plate.
In my experience the pen plater doesn't do as good a job as the regular
bath type plater, although it may cost less initially. If I had a choice,
and the money, I would invest in the bigger bath type system. I have seen
some use a regular rectifier, and modify a paint brush to use a pen type
plater, you could get the pen set up from Rio , and have the best of both
worlds. I think the solutions for the pen plater are a bit more
expensive, and you have less choices. Cyanide is nasty, and that is the
way you have to buy some of the pen plating solutions. You can get most
bath plating solutions in an acid base.