Why would you ever want multiple 2k's anyways...I haven't seen a good combo with them. Unless we're just talking about 2k 2k 2d instead of 2k 2d lol.
Also, what you can do after BBU in a combo is distance-dependent, but on every character, you can do something like...2k->2hs, BBU, 2d, 5k/5p/5s (sometimes you have to do 2 5ks or 2 5ps or 5s, 5s), jk j2k jk jc jk j2k jd. And if the height ends up weird for some characters it may not work, but this is the basic combo.