Choose substitute based on application: boards/sandwiches (Mahón), grating/finishing (Pecorino or Parmesan), melting (Aged Asiago), crumbling (Cotija).
Adjust ratio: use 1:1 for Mahón/Aged Asiago/Cotija; use ¾ cup Pecorino or Parmesan per 1 cup Manchego for cooked dishes to offset salt.
When using Pecorino or Cotija, reduce added salt in the recipe by about 25% and taste as you go.
For melting applications, pick cheeses aged 3–6 months or labeled 'for melting'—avoid very hard, crystalline cheeses (12+ months) that will be grainy.
If testing a new substitute, try a ¼ batch (test-batch) to check texture and salt, then scale up with adjustments.