Oh fir the Love of Christ, DO NOT "detail strip" your USP.
I have a USP40 with more than 70,000 rounds through it (it's a 1993). When I detail stripped it, it didn't need it--I had to replace a broken trigger bar or I wouldn't have gone as far as I did.
My son wanted his UPS 9mm duracoated in Desert Tan. Oh, it looks like a million bucks, but I took everything off, down to the mag release. Be advised that you need to make a special pin for the trigger which will hold the trigger and spring in place while you drive the pin back in from the correct direction (HKs go left to right).
Without that, you're screwed.
If you have not looked at the detail strip instructions--do it. You'll forget that you ever asked the question--trust me. Rotate this to here, push this to there, remove this. Then rotate this to there, push this to there, remove this--and so on. It's like a Chinese Rubiks cube.
Reassembly? Just reverse the order! <g>