I totally agree that sandals are the only way to go, especially when your feet are hot and sweaty. At this time of year shoe stores and Decathlon stock adventure sandals (adjustable at heel, ankle and toes) and they are perfect for continuing on with bad blisters.
If your blisters are unburst DO NOT put compeed style dressings on them as it will rip the tops off the blisters, risking infection.
If the tops are already gone, disinfect, trim up loose skin and apply a clean compeeds style dressing large enough to cover the blister adequately and leave on for as long as the dressing will hold. Open blisters need this to heal, if they are left dry they take forever to repair. Get some type of padded dressing/material (I used the fabric from the disposable room slippers that are supplied in Turkey) and tape over the top of the dressed area to keep any straps from placing pressure and wear socks to hold in place.
My husband suffered from regular blisters, until he finally purchased a pair of hiking sandals on the Portuguese at Tomar. He won't wear anything else now, even on winter Camino walking. I scored a nasty blister in March 2 days into the Lycian Way and swapped out to my hiking sandals with double socking and kept wearing them all the way to Antalya. They were so comfortable and secure and my blister healed without any disruption or discomfort on the most difficult terrain I have walked. I now have gone to the dark side and won't wear anything else for long distance walking. Look after yourself and enjoy the rest of your Camino.