Grips are easy to make. They are hard to make well.
I've made several for one of the guys here (as well as having made them for myself), and by far I now prefer having the grip frame to work from. Just not worth the compromise of working around Ruger's ever varying frames. I believe that is more a problem now than in the past, and you see it in their factory grip panels.
Back to them being easy though - yes, you really only need a drill press and some means of sawing and shaping. The more tools you have available (like a bandsaw and chopsaw) the easier it gets. I have a lot of power sanders of various types, I find a small inflatable drum sander and a 1" wide slack belt sander to be the most useful. Both do a good job of smoothing curves. Hard drums are also useful, but mostly for roughing, the hard drum leaves ridges at the edge of each pass.
The hard part is developing an eye for what looks right on the curves and the confidence to keep shaping down to those curves without worrying that you'll cut too much off and end up with a wasted effort. Those took me years to learn, but its worth it. Interestingly, learning these skills improved my work at the day job too - right is right in engineering, give up before its right and you'll be back to fix it later, sure as shooting. Too bad I could never get the professors to understand that!