Caulking up holes in your exterior walls is an important step in the pre-painting process. And so is choosing the right caulk gun. There are three main types: manual, battery-powered and pneumatic.
Manual caulking guns require you to push a plunger and pull a trigger. They may be cheap, but they can be messy, releasing caulk in an oozing, uneven stream that doesn't end as quickly as you'd like it to. Your best bet is to find a manual gun that has a smooth rod, which offers more control than its ratcheted counterpart, and comes with a built-in cutter to smoothly open the tip of the caulking tube.
Battery-powered caulking guns range from $35 to hundreds of dollars. For your purposes, a low-end battery-powered model should suffice. A gun that holds 10 ounces (283 grams) of caulk, for example, will be relatively inexpensive and less tiring to use than the manual version.
Pneumatic caulking guns are the most expensive. As the name suggests, this tool connects to an air compressor and is easier to control and activate that the other models. However, unless you're a professional contractor you probably don't need one [source: House Painting Info].
Whichever type of caulk gun you choose, it takes a little practice to squeeze a consistent amount of caulk. Ideally, you'll want a thin bead of caulk around windows, doors and chimneys before surfaces are covered with primer or paint.