I have hydraulic jacks. For what ever it is worth, I put the slides out, restart and level our coach with the engine at high idle. I don't like it to squat. I prefer it to remain at standard road height. By doing it this way, the air is pumped into the bags about as fast as the hydraulic leveling system is trying to dump it out. My theory is that the air system should be the primary support and the jacks can gently push it to a mostly level condition. My theory is NOT backed up by anything from Beaver or Monaco.
There are four reasons I do it this way. First is that it makes it easier to get to the bay doors under the kitchen slide. I don't have "Joey Beds" and have to crawl under the slide to get to my stuff. The second reason is that there have been times that the driver side living room slide has touched the dirt. The Beaver is so low to the ground to start with that uneven ground can be a problem. Third is that the sewer hose comes out at such a low point on mine that, if the coach squats much, the sewage has to flow up hill in many campsites-- and we all know how well that works. Fourth is that with the bags full I don't have to wake the neighbors twiice with a growling Cummins on mornings with an early departure. (If I had a Cat, the purr would be more pleasant!)
Regardless of how a I level it, if I hear creaking noises I will try something different. Maybe some wood under a low wheel or a different campsite. I haven't lost a windshield yet but I do have more than enough cracked tile. And, the front door (that has never fit well) works better without any twist in the frame.
