This is a video walkthrough of a Debt Waterfall problem from the Financial Modeling World Cup (this appeared in the July 2021 round). It's also a topic that's due to appear in the first round of the new season this weekend, so maybe it will help you get ready...
00:00 Introduction
02:50 Case description
03:57 Model setup
5:29 Revenue modeling
10:10 Interest rate calculation (interpolating between given values)
15:57 Modeling the senior debt with target DSCR
22:02 Modeling the subordinated debt
32:29 Modeling the revolver
34:20 Cash flow waterfall
47:41 Cash flows to equity and IRR calculation
52:01 Conclusion
You can buy the case materials (including the questions, instructions, Excel file with assumptions, and a worked solution) for $10 from the FMWC here:
https://www.fmworldcup.com/product/stage-7-2021-debt-waterfall/
(To be clear, I don't get commission or anything like that for referring you, and you don't need to buy the case to watch the video)
Waterfall icon from the noun project:
https://thenounproject.com/icon/waterfall-3838/