Any tried and true methods? Particularly across the instep.
I was once told to stuff them with wet/damp newspaper and to let it dry thoroughly. Any other suggestions?
Frozen water expands so...
Put a freezer-bag into the boot and part fill it with cold water. Twist the end of the bag and use a plastic tie to close it off. Put the boot into the freezer and leave it for 24 hours, then remove and allow the water to defrost. It should have stretched the boot and made it roomier.
It has never failed for me.
Get a hairdryer on the edge where you need a bit of a stretch, and gently, without getting too near the leather, push the handle of a wooden spoon inside against the part that needs stretching.