I used to go to the tourist information office in the town on arrival and ask them. More recently, I’ve used my mobile phone to find somewhere to stay, using the booking.com app. Other apps are available. Do you have a link to this other thread?
As an ex Guest House owner here is a couple of tips. By all means use the app to find accommodation then phone and ask to book. The app costs the owner at least 15%. Mention you are aware of the commission and ask for a 10% discount. If you get it fine and if not well use the app... you get your accommodation. Other tip is if you are leaving VERY early ask for a no breakfast deal. PH