At first I thought that it would be a pretty simple job, just assemble everything in Photoshop and hand it off to a printer. After getting quotes back from a few places (some over $1300) I was a bit flustered. I'd promised to make the project happen but couldn't believe how expensive it was to print. Then, I did a little research online. I found this project which gave me the idea: why not create my own scratch off ink and screenprint the cards myself? Then I could stamp them with the drawing on top and get them cut. By doing so much of the labor myself I could save my friend a mint in printing fees. Sufficed it was more work than I'd bargained for and ended up biting my teeth for a month waiting on printers, screenprinting, getting orders waylaid, and generally being tossed about on the choppy waters of fate but in the end I came up with some fantastic, beautiful, and pretty professional looking scratch cards.
I chose to do a pretty complex project, here, with all the aligning, cutting, stamping, screening and everything needing to work out so precisely to make the cards work. It was a bit extreme and in retrospect I wish I'd allowed more room for error but the principle is pretty simple. You assemble your design in photoshop, creating separate layers for each of the elements. I made sure to add crop marks to my page so things could be aligned at Kinko's for cutting.
I saved the design for the front and back of the cards as high resolution jpegs. I sent those off to the printer to get printed on cardstock. I made a transparency for the scratch off design to get made into a screen (you can find out more about the process here).
When I first sent the design off to the printer's they messed up a bit of my order. The design got printed on plain paper instead of cardstock. After getting a refund I added all of my order information (4 color printing, front and back, cardstock, my name, my phone number) in the margins of the print to make sure they couldn't mess it up. I've had mixed luck with printing so make sure you are really specific about what you're ordering and be sure to call and make sure they get your order exactly right.