Do a test. Use a piece of leather from the hide you are going to use for a project. Wet it well with a sponge, or douse it in water, water ever method you want to use to get it fairly moist but not saturated.
You can put it into a bag to case so the moisture content equalizes through the thickness of the leather. Some do this, some don't. Lots of options.
Set it out to dry until it begins to return to close to normal colour. It should feel cool to your face, means it still has moisture and surface moisture is still evaporating.
Use a couple stamps you intend to use. Stamp a small area and start keeping track of the time. Every 5 minutes, stamp a new area and record the time. Keep doing this until the leather is too dry and not stamping to the depth you want or the burnish you want. Pick the best time that had good depth and burnish. Use that, follow the same time for your practice or real projects until you get more of a feel for it.
Watch some YouTube videos by Jim Linnell.
He does a lot of instructional classes at https://elktracksstudio.com/
He normally wets his pieces using a sponge. The thicker the leather, the more he will apply. Then talks for a bit while the leather absorbs the moisture and equalizes. He will then do some tooling while explaining how and what. As the leather dries, he will sponge some more water on.
There are lots of ways of getting where you want to, to be able to get the depth and burnish you want. Lots of arguments / discussions about what people think is the beat and only way.
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