Thanks for writting in regards to my Doris Day font. To answer your question, my fonts are "donationware" and what I normally write is to keep in mind the size of the project and its repercussion. So I don't suggest an amount; it is really up to whatever your heart and pocket feel my font is worth.
A donation should be made through PayPal and my account there is: firstname.lastname@example.org
. Once the donation that is done you are free to use it in anyway you want.
P.S. Please, donate in Euros if this happens to be your local currency.