Another good thing to do with leather/boots is
bees wax!
Along with a few essential oils, and a couple other secret ingredients (found easily if you know what to search for). Anti-bacterial oils are best, but best not to start out with abrasive ones like tee tree, especially on older leather.
It's an old diy trick that was used by most farmers, herders and travelers as far back as probably the 17th century(?).
I've done it for two pairs of leather shoes/boots of mine. It works wonders.
They're nice and shiny
and waterproof enough; I wouldn't trudge through a river or large puddles, but walking in heavy rain is usually fine if you do it right.
For heavily used items such as shoes though, you've got to reapply it every month or two.
Just make sure to rub it in nice and thick.
Another trick you can do
with this is to line the seems with super glue or (even better)
Liquid Electrical Tape. LET dries fairly quickly and creates a rubberised, waterproof, almost insulated seal. I use it on a lot of stuff around the house, but it's
amazing for patching soles, heels and leaky shoes :