A few weeks ago at the drawing class I attend, we did mushrooms. I traced my sketch with a transfer pencil, ironed it on to a piece of cotton, and made this:
The brown marks are where the iron burnt the masking tape glue -- next time I'm using pins to hold it all together. The pink marks are the transfer pencil -- I gather they'll wash out, but I'm a bit wary of trying this... Better luck next time :-)