Preparing straps before sending through embossing machine question

[Amity]

I have recently purchased a hand crank embossing machine and some wheels to print designs on belts. 

My question is I have read a lot of information on embossing and I have noticed that people mention to "wet" the leather before sending it through to get the best imprint. Now when they say "wet" are they talking about soaking the straps in a bucket of water for an extended period of time, spraying it down with a squirt bottle, or maybe using a wet sponge rubbed across? No one really seems to elaborate on this.

And since I got you here I have another question that just came to mind. How much pressure do people usually use when sending the straps through the machine? I have done hand stamping and I know that takes a good amount of pressure. I am starting out with the BunkHouse poly roles. If anyone has any tips on using these I'd appreciate hearing it. 

Thank ya