I use ITA matrix (note you have to do this on a per-country basis, meaning when searching from A to B, where B is what you want, all airports in A have to be in the same country as A).

So say I'm trying to find flights to my hometown airport of DTW. What I usually do is pick an airport centrally located (or depending on what you're doing, you can use a more localized airport) and select the "nearby airports item" and change the filter to 2,000 miles. I then select all the airports I want.

It's not the best, but it does work.