My experience is all 3 must be horny, have found tremendous chemistry together, and be willing to try anything one of them suggests. The one to be DP'd must be experienced bottoming; it helped with my former 5-year regular that my cock's thickness had got him used to knowing how to take more than average. The 2 guys fucking do need to have above average length (7"+, preferably 8"+ topside) but not necessarily both with above average thickness. However, DPing with 2 thick cocks is particularly rewarding for all 3! Those who enjoy DP fucking are usually totally versatile or versatile tops. The one about to be double-fucked must be very ready & willing; some can take it at any angle. Taking 2 simultaneously to start is usually unnecessarily difficult. So, it's best if one of the tops starts fucking to get in; he pauses while little more than his cock head is in so the other top can get in, too. I still remember complex expression on my regular's face--briefly pain quickly replaced by a combination of disbelief & ecstasy. Meanwhile, it was so sexually exquisite for my Cock to be pressed against the 3rd guy's cock, occasionally sliding from our imperfect rhythm, while double-fucking my insatiable friend's ass! My friend was taller than for what works best, so it became awkward. With more space, though, we might've gone longer. We had been playing for a few hours already; so, we pulled out to finish with my regular face down & ass up. The younger, muscular, bi, totally versatile 3rd fucked until ready but shot his load on my friend's back (since he said he only came in his g/f); then he fondled my back & ass while I fucked until cumming deep inside. The more experience at least one of the guys topping has, the more fun DPing is!