Homebrew PCBs

I've just purchased a small heat press with a 4" by 8" pressing area.
It has a built-in thermometer which reaches a maximum of 250 degrees
(I presume degrees F since it was made in the US.)

The technique which I've discovered works well is as follows:

- let heat press warm up to operating temperature
- pre-heat copper board in heat press for about 15 secs.
- place toner image on copper board - I use magazine paper
- apply heat for about 10 secs
- run over the board with a small roller to ensure good thermal contact
- remove board from press and allow it to cool; remove magazine
  paper by running water over it

Magazine paper comes off very easily with water - just a little
rubbing with your thumb will take it off. Also, applying heat for more
than 10 secs runs the risk of enlarging your traces. Currently I'm
applying the heat press directly onto the magazine paper, but I'm
interested in using some sort of intermediate layer to help spread the
heat and ensure good thermal contact.