The simple question is: How important is a mash out?
Most of my mash schedules include a mash out, but is it effective? In order to do a mash out, I have to add additional water. Now the water column increases which - I assume - compresses the grain bed. So in that case, is a mash out really doing anything useful?
My impression, based on my system, is that it will wash out any left over sugars trapped by the grain bed. I have found that my beer has improved by sparging.
I like to gently stir the top of the mash bed while the sparge water is filtering in. I try to have at least 3 or 4 inches of sparge water on top of the mash bed, while it's slowly discharging out of the mash tun (try to match the flow rate)
There's a lot of variables to think about when getting concerned about a compressed mash bed - Crush of the grain, design of the mash tun. My only problems have been from using too much sparge water, because it dilutes the wort.
So, I'd say mash out is important - but a compressed mash bed isn't that important (unless it gets stuck)
also, having a pump is very handy, but you could feed it by gravity.