It only takes about a minute to drill an entrance hole. Funny thing is, I can still mess one up if I get in too much of a hurry.
I've ruined a few birdhouse fronts trying to get a good hole cut. Cedar is forgiving in a lot of ways, but it'll remind you pretty quickly if you rush it.
Things got a lot cleaner once I switched to a Forstner bit.
I use different-sized bits depending on which birds I'm building the house for. I've found that the way you drill the hole matters just as much as the size.
One mistake I made early on was drilling without a scrap board behind the front. Everything looked fine until the bit broke through the back. That's when the cedar liked to splinter. It didn't happen every time, but it happened often enough that I stopped taking the chance.
Now I clamp the birdhouse front and a scrap board together before I drill. It only takes a few seconds, but the scrap supports the wood fibers and leaves a much cleaner edge.
The other lesson was patience.
The last little bit of the cut is where I used to get into trouble. If I hurried the drill through, the edge almost always ended up rougher than I wanted. These days, I slow down as the bit gets close to breaking through.
Every now and then the wood still surprises me. A knot or a change in the grain has a way of saying who's really in charge, and the back splinters anyway. Then a little sanding is needed to clean things up a bit.
After drilling several entrance holes, I've learned that the hole itself only takes a minute to make.
Getting it right takes a little longer.