The least-risky method I can think of is to use a buddy; D-Dog's bark is very effective, but the problem is you can only tell him to stay where he is, not go somewhere else and bark. However, if there aren't too many guards, you can probably take them out. Additionally, I think that it will only attract one guard at a time. Guards seem to have this behavior where only one will volunteer to go check out a suspicious noise when not on alert, even if it was noticed by several of them -- as opposed to on-alert behavior where they'll automatically tell any nearby guards to form up on them. They'll pay attention to the guard while he goes to check, but remain at a distance.
Alternatively, Quiet is a good distraction if you have equipped her with an unsilenced rifle (and don't mind sneaking around with the base on alert). Have her shoot someone; I guarentee the guards' attention will be drawn elsewhere.
A riskier but more effective method is to use decoys. You can throw decoys like a grenade, and activate them like C4. They're very effective and cause guards to walk right up to them for a close examination before they realize it's a balloon. It will also cause ALL guards to walk up to the decoy, not just one of them like the aforementioned suspicious noise. Right-clicking while in the box allows you to pop out of the top very quickly and begin aiming your equipped weapon. Usually, guards aren't looking at the delivery point even if they're next to it, so you should be okay to pop out and toss a decoy before hiding again. Just be sure to take out the guards inspecting the decoy if you don't want CP to be aware that you've infiltrated -- they'll report anything suspicious.
If you're going for takedowns, a viable option might be sleep grenades. They're quite risky to use but very effective. They have a fairly small radius, so be sure that the guards are all close together -- and be sure not to walk in the gas yourself! Also, if the guards are wearing gas masks, the sleep gas will be ineffective. However, they do take effect immediately on the guards and don't make any noise. If you plop it right in front of their faces, they might react fast enough and dive away from the gas cloud, though.