How can a small manufacturer build a reliable rolling cash flow forecast?

[Ava79]

I've recently taken over financial planning for my family's small manufacturing business, and while our P&L looks stable, I'm realizing our ad-hoc approach to cash flow forecasting is a major vulnerability, especially with seasonal demand swings and longer payment terms from our big clients. I've set up a basic spreadsheet model projecting receivables and payables, but I'm struggling to accurately factor in variable costs like raw material price fluctuations and unexpected equipment repairs that can really disrupt our liquidity. For other small business owners or financial controllers, what methods or software have you found most practical for creating a reliable, rolling cash flow forecast? How do you build in contingency buffers and scenario planning without making the model too complex to maintain, and what key metrics do you monitor weekly to catch potential shortfalls before they become crises?