I wear sandals all year round, you just have to wear socks, as per the gloves on your hands. If your shoes are normalish leather, they can be hydraulically stetched. Toes, like asses on Brooks, are rarely tough enough to easily stretch out the leather that offends them.
Pinarello Road, Surly LHT, Dolan Track, Fuji Supreme, Guru Ti Tri, Bamboo
All cotton socks give me blisters sometimes. Smartwool socks have a no blister guarantee. Avoid vasaline, try an anti-chafe stick like Body Glide. It doesn't get gummy when you sweat. Triathletes use it on every body part that could possibly rub.