Tommy,
Note that I said "almost" a couple of times because there will be some challenges. But it's usually not that difficult, but practice does help you gain confidence. Also, note that using any technique to try to 'classify' a potential bottle cap or similar iron-based hunk of junk, that is a challenge if the cap or target is too deep. Usually, bottle cap will be located within the top 3" or so of the soil and that will make it easier.
Note, also, that a DD coil can be more difficult to use due to the winding characteristics, and DD's are known for not discriminating as well as a concentric, especially closer to the coil. I do find the 5" DD a lot easier to use in heavily littered sites, and most often quicker to use to classify a bottle cap than I do the 11" DD coil.
If you have both the 5" and 11" DD coils for the G2, work with both until you master how to use them to their fullest to classify a potential bottle caps since they ought to read as Iron .... once classified. As mentioned below in some another post by 'capt.', you can read my Tips & Techniques on Audio Target Classification on our website. It is printable. just go to www.//ahrps.org/ and click on Tips & techniques. You will find it there.
If you have questions while working with it, just e-mail me at monte@ahrps.org.
The G2 is a very good detector. I have used it with every coil made for the Greek series and it worked OK for me, but I do prefer either the 5" or 11" DD coils on it for the general tasks I have depending upon the site.
Monte