Any/all of the finishes get hard from contact with Oxygen.
Use some and the space in the can fills with Oxygen right?
There's a trick to displace Oxygen in a can with CO2.
CO2 is heavier than Oxygen.
Mix baking soda and vinegar and it fizzes right? The gas being made is CO2.
Tools;
Aquarium tubing
Empty large dish soap plastic bottle
Baking soda
vinegar
long story short;
Rig up the tubing to the top of the bottle,
get he baking soda and vinegar fizzing and direct the end of the tubing into the can.
I place the cover on the can, and just put the hose in a bit, when the mix is about fizzed out, squeeze the bottle for more CO2 then just slide the lid over and tap it closed.
The learning curve;
Don't use too much vinegar/soda or it'll spit out the tube
Learned that trick a few years ago, works great, and has saved me a bunch of money not having to toss crusted over or dried product.