I've been prompted to make this quick video about one use for the hand plane after a couple of customers asked why we supply our fretboard slightly wider than the necks, as they felt this was a real problem for them. Trying to glue-up-a fretboard and neck of exactly the same width is very difficult to get-bang in terms of accurate alignment, so its easier to use wider fretboard and trim it to width after glueing. A hand plane is the ideal tool - it's quick, easy and very accurate.
I think a lot of people making cigar box guitars are scared away from using such basic tools as they perceive them to be difficult to use and only for experts, but ironically seem to be willing to consider buying and using very expensive and potentially dangerous power tools, even when they have almost no practical woodworking skills at all. I am a great advocate of learning to use hand tools properly before moving onto power tools and fixed workshop equipment, as having a feel for how a tool is cutting the wood is at the heart of accurate and safe woodworking. Many power tool accidents happen because the user has no experience or feel for the rate of feed or how the wood is behaving under the powered blade...with a hand tool this feedback is instant and natural and very low risk. Once you have acquired this knowledge and feel, it makes using power tools so much safer, as you are far less likely to to push too fast when cutting or take off too much in one pass when planing because you will have the feel and knowledge of how the timber will interact with the moving blade.
Alongside the handsaw and chisel, the plane is one of the most basic and useful tools for guitar making - they are cheap to buy. There is a huge amount of information out there on the web to help you sharpen the blade and set-up a plane - it's no mystery and just needs a little patience and diligent application. I'm using a Stanley No.4, which I find really handy, as it is light enough to use one handed (although I don't recommend this until you are comfortable with using it with two hands), but long enough to be accurate along the length of the edge of a guitar fretboard. Buy one secondhand, clean it, oil it, sharpen it & set it up and you'll be good to go, with a trusty life-long workshop companion. A powered hand planer is nowhere near as pleasant or safe to use, and will produce an inferior job, as you have very little control of the speed and depth of cut. It's a crude and brutal tool compared to a Stanley or Record bench plane.
I've got a workshop full of potentially dangerous power tools such as a bandsaw and a surface planer/jointer, but for this simple job there really is only one tool for the job, the traditional hand plane. www.chickenbonejohn.com