Quote - If you set the blend to .25 will it mix input 1 by .25 and .75 of input 2?

 

Not quite but your thinking is perfectly accurate with regard to how the number influences the blending.

Think of it more as a slider with "0.0" being the Input 1 end and "1.0" as the Input 2 end. The blend value is how far along the slider you're setting it, so 0.25 will mean that it's nearer to Input 1 than Input 2. In numerical terms, 0.25 will result in the output being 75% of Input 1 and 25% of Input 2.

 

Quote - The math function next to it, that should always be set to multiply followed by the bump map correct?

 

That's multiplying the image map values by the number you entered in the "Use custom bump value" when running EZSkin. It lets you adjust the strength of the image map on the overall bumpiness (reducing it by putting in a value from 0 to 1; increasing it by putting a value greater than 1). Changing the function to something other than Multiply will change the effect that your entered number has on the image's bumpiness. Which could be useful in some situations, I guess, but generally just leave it as Multiply.