The most important way you can help out this cause is to simply order a stamp and start stamping bills:

Product image of the Trodat 4927 stamp to be purchased Standard, Self-Inking Stamp
Model: Trodat 4927
Ink Color:
Product image of the cheaper, wood-mounted stamp to be purchased Cheaper, Wood-mounted Stamp + Inkpad
Model: 1 in. x 2 in.
Ink Color:

So you can make it rain these things:

This is the design offered:

To prove that isn't about profit-making, we offer an alternative: order the stamp yourself from a 3rd-party vendor, bypassing This offers the additional advantage that you can customize the stamp however you want; edit the text, get a fancier or cheaper stamp model, start your own version of, whatever you want! Here's the tutorial (Cost: $23 [free shipping!])

And once you have a stamp...

Here are some stamping tips.