press n peel blue paper
i used both the coated paper version and the blue stuff, and the blue sheet works much better. i think the coated paper is lightly waxed paper and a thin coating of elmer's glue. you're supposed to print to the sheet, iron to the board, and soak in water to release the paper. If you get old paper it doesn't release so well, or the toner just likes to stick to the paper better than the board. This may also happen from too much heat, so be aware if you see it.
Peeling the blue stuff leaves a very nice coating of blue stuff on top of your toner lines, giving good edges and very little overetch even for thinner lines.. But they charge TOO MUCH FOR IT!!
things i found with either.
1) CLEAN YOUR BOARD. Use steel wool with soap embedded or add "comet" cleanser, but you want that "pink" surface or neither sheet will stick so good. PS-dry well! you can even use acetone or IPA to remove any excess moisture, then blow dry with compressed air.
If you screw up a iron-on, do this again to scrub off the toner, or use acetone to strip the toner, then scrub.
2) More heat is not always better. My first couple times I ironed at very high heat for too long. It bakes the toner into rock-hard lines that either stick to the paper (especially the coated paper one) or crack apart on the board. Then I used a professional roller that simply ran the whole board thru a hot roller. Stuck great, but I dunno the temp.
3) I found for either style, ferric chloride was a nicer etchant than the ammonium sulfate??? stuff. Much uglier and messy if you drip some on the table, but a very good etch. Use either one hot (70-80C)if you can for best results..
Supposedly you can print to "Transparency sheets" which are made of hi-temp plastic - then iron onto a PCB, but i never got it working too good. My toner did not cover the dark portions completely, so it ironed on OK but my ground planes and lines got way overetched. That was on crappy toner though..
let me know how it goes - feedback helps everybody!