We need to create interunit payments

We used bilateral netting to handle payments within the same BU successfully. Now we need to make payments from one BU to another BU - without actually cutting a check, just transfering the funds on the GL. We believe this is achieved using internal banks, the documentation explains the mechanics of setting up the internal banks, but it's very confusing how to actually set up the scenarios.

here's our scenario;

1. we created the bill out of BU01 for 100.00

2. we want to create a payment out of BU02 for 100.00

in the end we just want GL entries to show the accounting for these transactions, but not create actual cash payments. Any guidance or experience would be wonderful.