How to pick up weapons fast and reliably? (to beat IW time for O Cristo Redentor)

When I'm running and the message "press and hold X for " comes up, and I press it immediately, I always miss it.

It works when I anticipate and start holding X before I reach the weapon.

But when I kill an enemy, the "hold X" often flashes up only for an instant, then disappears. My theory: you can grab it in the moment they die, but then they drop/throw it. So I tried holding X as I kill someone, but this mostly results in a (lengthy) reload.

Is there a trick or technique to it?

I'm trying to beat the IW time of 1:16.20 for "O Cristo Redentor" (MW2, spec ops, Alpha). My best time is 1:30. I average 2:00-2:30. This incredibly impressive video does it in 0:47.35. A key technique is picking up weapons, and not reloading (plus skill and luck). He's on PC.

EDIT I realized he (klooger28) has a bunch more runs.... including doing it in 38.10.

EDIT2 using that approach (anti-clockwise, picking up dual, and alternating reload hands), I got 1:19... almost there!

BTW: Sometimes there's a weapon's image on the ground, but I can't pick it up - a glitch?

Sometimes it seems I pick up ammo instead of being able to pick up the weapon - I guess this is when the weapon is the same as my present one (or maybe some use the same ammo?). Sometimes, it seems like it might be my secondary's ammo. I guess the only thing is to recognize then it's the same weapon.

I must have tried over 100 times, and can't find anything with google but the above video ... please help!

I'm playing on an Xbox 360 if that matters.

I remember doing that in like the 4th or 5th attempt without that specific technique. I used a two hand p90 (if memmory serves) and did that alternating reload hands thing, since the clip is really long I didn't even change weapons.

The glitch is not, you got it right, is the same weapon you already have and the same specs (Red Dot, Acog...), since it's the same you have, you can't pick it up, you pick up that ammo though. You even pick up the ammo of another gun same as one you carry even if they have different sights or handle, or the underbarrel.