User blog comment:AYET/About imbued Busoshoku Haki/@comment-109.67.192.44-20121102131616

It was imbued with logia. Most attacks would be usless against Logia if it weren't the case. Imagine when a swordsman has to always stay in contact with his enemy in order to hit him - just no.

Mihawk used haki in the Marinford war in his attacks, just to make them stronger. Of course you can imbue it in other attacks - like guns, if you can't imbue the bullet with haki what's the point?

About logia powers, I'd imagine they depend on haki. Think about Ace and BB's fight, or Akainu and WB's I think they probably used haki to enhance it or else it would be a little too uncotrollable a variable to make much sense.