Doing your own grinding is not difficult at all, doesn't take much extra time, and well worth the time spent. The two most common types of home grinders are blade grinders and burr grinders. Blade grinders have a rotating blade that chops the beans like a food processor would. The ground size is determined by how long you have the blade whirling for. The problem here is that the grind size is very unstable. It is hard to achieve the same grind size each time, and some of the coffee may be turned to dust while other pieces are still coarse. Using several second pulses of the grinder blade instead using one long grind helps alleviate this problem but certainly does not solve it. To get a rather consistent grind, one needs a burr grinder.
Burr grinders have two sets of rotating teeth, the distance between which can be adjusted and set. (We supply both types of grinders, we carry a good beginner home burr grinder for $40, and with a lifetime warranty). Even with a burr grinder all the grounds are not even and one must take can to keep the burrs sharp and have a motor with a low rpm. So why all the bother with ground size? Because different brewing methods perform better with their corresponding ground size, and different coffee drinkers will prefer coffee based on the method and ground size used. Generally, a safe rule of thumb is that the longer a unit water is able to contact the grounds, the coarser grind size you want. Therefore grind size for espresso (about a second of contact time) is finer than for drip brewing, and drip brewing is finer than for French-pressing (3-6min of contact time). Vacuum brewing is kind of tricky because the contact time can vary quite a bit, I generally grind a little finer than for autodrip.
Personal preference is also a factor in these types of brewing, some may prefer using a coarser grind for their vacuum brewing than others. If you grind at home I urge you to grind you beans significantly finer for a brew and note the result and your preference. Just make sure you don't grind them so fine as to prevent the passage of water through them.