Nobody gets 14 presses. Boss gets ~12 presses he says, but he mains doc/mario, though I hear his Luigi is beast.
You only need like 8 presses to get a good benefit, and 10 is pretty good, so just keep at it.
As for practice, do practice on CPUs, just don't keep practicing the same combos over and over so you don't get into bad habits. Comboing CPUs is REALLY important so you learn what moves will lead to other moves on certain DIs at certain percents, how to move as fast as possible during combos, and the ability to execute any move you need to on the fly on reaction to their DI. Level 1s tend to do no DI, but once in a while they DI randomly.
Hilariously enough, comboing fastfallers with Luigi is really similar to comboing players with Luigi a lot of the time. I've played plenty of good players who miss techs/DI on Luigi's stuff and let you do that nonsense you do to level 1s. If the players aren't that good, then it'll happen really often. After you get that stuff down so you can do it in your sleep, then you can start learning what to do if they actually DI/tech correctly by playing matches and experimenting, since hopefully you'll have a foundation of tech skill and feel for his moveset to work with by that point.
As for practicing the WD cg specifically, a trick Vist told me about is to go to training mode and set the CPU fox to evade.
Finally, the applications for up B that I find are practical are:
-punishes for sufficiently laggy moves.
Jiggs' rest, Marth's non tipper fsmash or Link's up B if you shield them, and Peach/Sheik's dash attacks on your shield are the most common ones I can think of. ESPECIALLY Peach's dash attack. It's her best ground move against your wavedash approaches, so often times you can bait this and really get her for it.
I've seen Pakman get Scar with up B oos when Scar kneed his shield, though Im not sure if that's supposed to work.
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punishing laggy recoveries. Most commonly used vs. Sheik, but you can also do this to Marth if you lightshield edgehog him. It also works in Luigi dittos if you grab the edge and they missile onstage instead.
I've gotten Vist with this plenty of times in tournament. Of course they can choose to not recover onstage, but then they risk getting edgehogged or hit by a ledgehop/ledge drop dair, etc.
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nair -> up b on platforms on Fox/Falco. When they have to land on a platform, usually the top one, if you read where they are going to tech you can do a rising nair through the platform. Time it so that it hits them weakly and it pops them up just a little bit, perfect for you to land and then do a grounded shoryuken. The aerial shoryuken is almost useless.
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techchasing. this happens most often when you get a WD ftilt that knocks them to the edge of the stage. If you just wait, or maybe do a little faking (WD in place, dash forward WD back, etc.) a lot of the time people will either tech roll or grounded roll towards you, in which case you can get them with up B. If you've ever seen Jiggs players bait rests this way on techrolls towards them, it's like that.
Or, if you get enough momentum with your WD ftilt, you might even slide to where they land and get to up B their missed tech, as in that Pakman vs. Jman match.
http://www.youtube.com/watch?v=0HARB4gr2js#t=3m13s
You can work it in on the fly in random situations too, like this maybe:
http://www.youtube.com/watch?v=i2Y9voCAULk#t=10m10s
Or this:
http://www.youtube.com/watch?v=5EminDG_j8c