I saw the term in in this question. I think I have an idea, but not sure if this a localized term or if wide spread meaning for the term.
Shotgun would implie that he might be (over) using a tool or technique much bulkier or clunkier than a simpler, more elegant solution can be found. And voodoo?
Shotgun implies blindly scattering a million little bits of junk all over a problem, like the pellets in a shotgun shell; hopefully one little bit hits the mark. It's trying stuff until something works, rather then understanding what's going on.
Voodoo implies doing something because of magical beliefs, or more specifically, doing something for an unknown reason, especially something overly complicated: "I've always done it this way, I don't know why it works."
Neither characterization is flattering: they imply ignorance and incompetence.