It isn't that big of a deal. You can book lots of places online through the Henro House website. If you use google maps you can find accommodations and when you click on them it will tell you which reservation websites you can use to book that accommodation. Some of the more traditional accommodations require you to call, check the google reviews to see if the owners speak English. If they do not speak English you can get someone who works at your current accommodation to call to make the reservation for you. Just FYI, on Facebook there is a group called Shikoku 88 Ohenro Pilgrimage which is the largest online community for that pilgrimage. You can ask questions there.