I mix once in a while. When I do I fill the basked 3/4 full of briquettes and then the lump goes on top. Lump usually burns hotter, has less ash and doesn't last as long. That's why I put it on top. Gets the cooker up to temp faster and the ash doesn't smother the briquettes underneath it. Prolly doesn't make a hoot of difference but it makes me feel "smart". Cheers!!!
If Homebrew & BBQ aren't the answer, then you're askin' the wrong questions... Cheers!!!