woah okay well first of all welcome to SWF. i recommend watching some vids and reading stickies, brawl tactical discussion, and using search before you post "new techs" because most of them are discovered. if you have a question, chances are you're gonna find it was already asked.
to do a short hop it isn't really a matter of sliding your finger off of the jump button (x or y... i wouldnt recommend tap) as quickly as possible. try going to training and jumping around.
ken combo is not supposed to be possible in brawl because characters can DI (directional influence... they hit the control stick to affect their direction from their hit.) or airdodge before being hit. the way the ken combo WOULD work would be grab>forward throw>short hop>fair(forward air)>another fair while you're still in the air. try just holding forward and mashing a until you hit the ground. then doing fairs until you get them to the edge, then follow with just one fair, then jump, and do a dair (you must tip the dair to spike).
many would say marth's spike is not good because it's so hard to hit with, but if you practice you can get good at it. i personally have MANY different tactics of landing spikes. you may not know what these terms mean so you can look them up. i like footstool spikes, ledge hop spikes, back spikes are easier to hit because of the bigger hitbox, front spikes you will get the feel for. always dair on your way up after a jump unless you do this: hold down while you're on your way up then c stick the dair so that you don't fastfall. then use your second jump and upb to recover. you can also set up spikes with d-tilt, fthrow, fair, and forward b.
i can't exactly say who the BEST is, but i can name some great marths. Emblem Lord is probably one of the most knowledgeable marth on these boards, there's drago (watch his combo video on youtube: redemption), Roy_R, and many more. WOOOOW i just typed a lot.
Once again, welcome to SWF and I hope this was useful.
