Preparing for our trip to Cyprus, we noticed that very little practical information (opening hours, ...) can be found about the painted churches, so maybe the below is useful for future visitors. Note that we visited all 10 churches mid March, so potentially the opening hours may be different in other months/seasons.
As mentioned in previous reviews, it's best to use GPS coordinates to find the churches - they are indicated below. Unlike Clyde, we never felt we needed a 4x4 vehicle but the difference might be that we used the 'avoid unpaved roads' option on our GPS.
We explored the Troodos mountains for 2 days. Visiting all 10 churches in one day could maybe be possible since we departed from Nicosia and also visited other sites (Kykkos, Fikardou, ...), but this will probably be rushed.
We particularly liked the churches located outside of a village (e.g. the ones in Nikitari and Platanistasa), but they are all worth a visit.
1. Nikitari: 35°02'45.4"N 32°58'24.5"E, open when we visited it on a Monday at 10 AM.
2. Lagoudera: 34°57'55.7"N 33°00'25.1"E, open when we visited it on a Monday at 10.45 AM.
3. Platanistasa: 34°58'44.8"N 33°02'48.0"E, closed when we visited it on a Monday at 11.30 AM. Coming from Lagoudera, a sign at a T-junction (right to Platanistasa, left to the church) indicates that the key can be picked up in Platanistasa. We did not do this taking into account that this would take about 30-45 minutes (back and forth) and that we were low on fuel [note that there are not a lot of petrol stations in the Troodos mountains].
4. Palaichori: 34°55'18.7"N 33°05'41.9"E, open when we visited it on a Monday at 12.15 AM. However, note that the church is normally closed on a Monday but we were lucky that other tourists called the caretaker. This person also gave us a 10-15 minute explanation about the church, the paintings, ... which was certainly added value.
5. Pelendri: 34°53'35.4"N 32°57'58.8"E, closed when we visited it on a Monday at 14.45 PM and no coordinates of the person with the key.
6. Galata: 35°00'12.5"N 32°53'47.7"E, closed when we visited it on a Tuesday at 9 AM. On the door is a telephone number which can be called as from 9 AM but when we tried this at 9 AM and again at 9.15 AM there was no answer.
7. Kakopetria: 34°58'39.8"N 32°53'20.1"E, open when we visited it on a Tuesday at 9.30 AM.
8. Pedoulas: 34°58'03.4"N 32°49'52.8"E, open when we visited it on a Tuesday at 10.30 AM.
9. Moutoulla: 34°58'56.8"N 32°49'26.5"E, closed when we visited it on a Tuesday at 10.45 AM and no coordinates of the person with the key.
10. Kalopanagiotis: 34°59'33.4"N 32°49'48.4"E, open when we visited it on a Tuesday at 11 AM.
Finally, note that in most churches taking pictures inside is not allowed. However, the caretaker at Palaichori did not mind and in Pedoulas there was no caretaker at all.