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keeping good circulation
I think that's why my missus has warm hands and feet while I suffer. My blood is like porridge - thick and lack red blood cells.
I had the Lezyne, Woolie Boolie which I didn't use and PlanetX merino. I'll have a look for Smart Wool and Darn Tough - I think I might have a Smart Wool pair already I've used for hiking but they're too thick for the cycling shoes.
https://www.amazon.co.uk/Smartwool-Bike-Zero-Cushion-Socks/dp/B0BKWWHZMY
I see. Tricky.
Corn starch and single light weight merino wool socks would help keep your feet and socks dry in the day. If your shoes don’t breathe well, you could vent shoes, change socks and/or dry toes and refresh corn starch as needed towards night. An alternative would be heated inner soles to use at night, but if your socks are already saturated they might just delay the pain.
IME, the key on hikes is keeping good circulation, and keeping toes dry(ish). You’re mindful of your tendons being constricted, so I suspect you’ve thought of shoe fit too.
I’d try taking spare socks. Merino can be hit and miss, so paying extra (£20 ish, look for sales) for the established brands is safest bet. I have a pair of REI quarter length light weight hiking socks that are entering their 10th year and have been from Canada to Tierra del Fuego. Smart Wool and Darn Tough are dependably good. Conversely, there’s a £45 pair on Amazon from a brand I can’t find elsewhere, and I wouldn’t recommend.