A seller on eBay has sets of 10 fabric paints pens for £2 all in and they sure are worth their weight... we really managed to spice up and personalise some old ragged t-shirts.
Heres what we did ....
First we printed out some extra large letters onto normal A4 paper. Then put greaseproof paper over the letters, traced them and cut out the inside. During this process, we made sure that the shiny side of the baking paper pointed downwards so as to stick onto the shirt during ironing.
Then I ironed on the letter outlines with the iron on full heat and steam function off.
Then the kiddies had their fun and scribbled bright colours all over their letters. (note- my particular make of greaseproof paper wasnt always holding well, so i eventually reinforced it with sellotape)
After the paints dried we peeled off the tape and paper... and voila!
Other designs were also made by using masking tape stuck vertical and horizontally across the shirt. This one is not bad considering and 18 month old painted it!!