None of the PCs have ever purchased magical healing from a church, so you are not familiar with how to do it. Enough adventurers pass through Hommlet that probably all of the churches have a process for selling healing to those who are capable of paying and meet whatever other requirements the churches have (follower of the God, etc.).
The Church of St. Cuthbert is the largest Church with four priests and two holy warriors. Canoness Y'Dey is quite well known. It is well-known that Canoness Y'Dey, while being dedicated to fighting evil and an exemplary lawful good character, is not charitable towards adventurers, and thinks that adventurers should pay their own way. She only "gives" magical healing to the poor and those unable to pay.
The Temples of Pelor and Ehlonna are much smaller and have only a single priest each. The Grove of the Old Faith has three Druids (including Belaver).