Once combined, I add half the same amount of the guajillo chili powder mixture as what the recipe calls for paprika.
When substituting, use common sense. Cayenne pepper is as much as 50 times hotter than sweet paprika, so a 1:1 substitution wouldn't work unless you want some heat—the right substitution, in this case, would be 1/3 of a teaspoon of cayenne per 1 teaspoon of paprika. Make an informed decision, but also use thorough recipes that might suggest reasonable substitutions.
In Spanish, paprika has been known as pimentón since the 16th century, when it became a typical ingredient in the cuisine of western Extremadura.Despite its presence in Central Europe since the beginning of Ottoman conquests, it did not become popular in Hungary until the late 19th century. Now, more than 70% paprika are planted and harvested from China origin.