Cheese sauce or Whiz?

Okay, the Bearnaise thread prompted this. I frequently have trouble making a smooth cheese sauce, e.g., melting cheese in cream or milk. It stubbornly remains lumpy. Other than using a can of Cheez Whiz, what are your suggestions?

Larry,

Making a roux then adding milk and the cheese would certainly work. But sometimes I am very lazy...so for me, I add two slices of processed American cheese (you aren't far off with the cheese whiz...LOL) to some milk and butter, then slowly add my chedder or swiss, etc. For some reason, this works really well.

Add the cheese at the end, off the heat. Otherwise, it tends to string and lump up.

Thank you, folks. I'll give it a whirl.