Staples "Picture Paper" (30-sheet package): item #471861. It is $9.99 for 30 sheets.
www.staples.com
it cost me:
$9.99 for the paper (30 sheets)
$4.00 for the boards (2-4x6)
$3.99 for the etchant (16oz)
Knowledge gained PRICELESS!
I printed the toner transfers 6 on a page at work. Cut them out, 2 minutes of ironing. Soaked in hot water for a couple of minutes then rubbed the paper off and used an old toothbrush to clean off the rest.
The first board with cold etchant took 20 minutes in a plastic container rocking back and forth. the next 3 took less than 10 after I sat the container in a sink with HOT water.
I don't think a double sided board would be that hard. I would iron 1 side to the board then drill 4 holes (maybe 2 would work) thru the board at opposite corners. Drill the other side toner traces int he same spot then use jumper wire to align it long enough to iron a couple of spots on the board to secure the toner sheet to it. Remove the jumpers and iron it on and continue as before.
If you look at the boards I made after they were etched, there are initials etched on the boards the upper left was my first try, Sharpie marker was on too thin but the others turned out great.
I am going to try roughing up the front of the board with sandpaper (fine) then printing the front silkscreen with yellow toner (work again) and ironing it on.