Ask HN: What do you use to manage your affiliate programs?

I quietly rolled out a small affiliate program to a few of my power users on SnailPad (www.snailpad.com) and, for now, I'm tracking payouts on a spreadsheet and planning to manually send out payment via Paypal. Anyone tips on how to manage this stuff over the longer term?

FWIW, I'm paying out 20% of the referral's first monthly payment and then 5% of their on going payments. I gave myself a 45 day window to make sure I don't shoot myself in the foot when it comes to cash flow... so I have about a month left before my first payments need to start getting paid out. I'm really hoping that I either find a better solution or I build something in house to avoid having to manually deal with this stuff day-to-day.