Choose the substitute based on your dish type: cayenne or DIY blend for smoky cooked dishes, Thai bird's eye for high heat, chipotle for deep smokiness, fresh Fresno for fresh salsas.
Prep the substitute by grinding or mixing as needed; for the DIY blend, combine cayenne and smoked paprika in a 3:1 ratio.
Apply the substitute using suggested ratios: 1:1 for cayenne, 75% volume for Thai bird's eye, half volume for chipotle powder, equal whole chili volume for fresh Fresno.
Adjust seasoning and taste as you go, especially with hotter substitutes like Thai bird's eye chili.
Use fresh Fresno chili last in fresh applications; avoid using fresh substitutes where dry heat and smoky flavor are essential.