Well, a couple times a week for a few years - I've practiced a bit! :-)

Makes sense to cook the lamb separately. I haven't had any sizzling problems with the grease, I think because the fat stays on top and the tap water doesn't get hot enough to evaporate.

I get the lamb from a farmer's market vendor for an individual farm, and their fat content varies a lot, from not enough to bother pouring off, to a solid 1/4 inch on top of the water in my little bowl. The vendor said they aim for 20%.