Below is an overview of the tools I use to apply joint compound to either drywall joints or plaster walls. While the type of joint compound you use will differ depending on your situation (read my post Patching plaster cracks with joint compound), the tools basically remain the same.
A mud pan is where I mix my joint compound when making small batches, like the plaster wall crack repair in my upstairs bathroom. The narrow design is easy to hold in one hand as you gather mud with one of the various joint compound applicators shown below. As you can see to the right, a few years ago I went the cheap route and bought a plastic mud pan. I probably saved about $10, but I now regret it. Spend the extra money and get a stainless steel mud pan, it’ll last forever.
My plastic mud pan has been used so much it’s developed some small hair-line cracks which I’ve repaired with thin strips of styrene plastic (.020" thickness, found at model railroad hobby shops) glued onto the crack from the outside of the pan. Again, spend the money upfront and buy the better one. Never skimp on tools, you’ll only regret it later.
UPDATE: Read my February 4, 2007 post, Stainless steel compound mud pan, to see the right type of mud pan to buy.
4" joint knife
This is the tool you must have when applying joint compound. It’s used to mix the joint compound in the mud pan and to put the first layer of joint compound onto the drywall or plaster.
6" taping knife
Once the first layer of joint compound has dried, move to a 6" taping knife. The difference in the width will help taper the joint compound out over the wall. Most taping knives have blue spring steel blades that are sturdy, yet have some flex when you’re pulling the mud along a seam.
10" taping knife
Hopefully, the final step will be a third coat of joint compound with a 10" blade.
Inside corner tool
To apply joint compound to an inside corner, use the aptly-named inside corner tool. (There’s also a similar tool meant for outside corners, but I don’t have a need for that application.) The blade of the inside corner tool are set at the perfect angle and make drawing mud down a corner extremely easy.
I’ll show more specific examples of how to use joint compound tools as I progress with patching the cracks in the upstairs bathroom.