Doing veneer with hot hide glue (hammer veneering) is very different from vacuum pressing. One problem that I was attempting to alert you to is that certain veneers are not well behaved when worked with hot hide glue because of the water content in the glue.
Pressing veneer with hot hide glue is a special skill. You may like it, or you may not.
The commercial glue pots regulate the temperature pretty well. I'd have to go look at the documentation but 140 degrees sticks in my head. I tried putting water in the pot, then the hot hide glue in a glass jar sitting in the water. Other people have reported good results with that, but I had problems. The glue in the jar just wouldn't get hot enough. Maybe if I left it sit longer it might have worked. People do that when they only want to mix up a small amount of hot hide glue. I just put it in the pot and worked it from there. It's not hard to clean the pot - the glue is water soluble and cleans up pretty easy.
Mike