It sounds to me like when you say "add a delay to each track" that it is misleading a little. I assume that what you mean is that you want the multiple tracks to not all be "spot on" to give the guitars a thicker and more layered sound. If this is the case, what the other guys reccomended will work, but there is another way that I think is a little more effective, and probably less cluttering and quicker and easier way to do it. If it were me and I wanted to do this, i would just drag a couple of tracks a tiny bit. This saves the setup time of properly setting a delay plug in as well as saving on some cpu headroom. Basically, all you are doing with this method is offsetting the track a little bit to "thicken" the sound a bit. What you have to watch for is the phasing that this creates. You have to listen carefully, and panning the original and offset tracks away from each other can really help to reduce the amount of perceived phasing. Also, keep in mind that phasing is often times referred to as a bad thing. This is not always the case. Phasing is a fact of life that will always exist, even between different instruments. There are many factors to consider like timbre, timing, pitch etc... that can all contribute to this. Just use your ears and decide which sounds better, but you may also want to do a quick "mono" check to make sure that the mono image is not being collapsed too much as a result.
If you are layering by actually playing each track multiple times, I would consider not offsetting the tracks. You (or any human for that matter) should not be able to play so perfectly accurately that there is not a thickening effect from the imperfections between the two tracks. I would also try layering the second track with a different guitar, pickup position, amp etc... to add some contrast. One fun trick I like with heavy guitars is layering a clean track behind a distorted track. This can help regain some of the dynamics and punch that amps lose when they have too much gain applied.