I've just come across this YouTube video featuring Corinne Brad, including a great demonstration (which starts at 4 minutes and 25 seconds in) of how to use rub on foils.
The pen that Corinne is using is very similar to the Tonertex Write & Rub glue pen, the Sakura Quickie glue pen also works in the same way.
Foil Play stocks a huge selection of rub on foils, available to purchase individually or in kits.
Tim's feminine side
23 hours ago