To tech you need to press the air dodge button 20 frames before you hit a wall, which is basically just as you hit it. Look up how to play lucas 101 by alpharad, that will show you how.
As for ness again no, never do pk thunder in air again, its like going outside mooning everyone, your asking to be arrested. Also the ending to Shulk vs Ness where you tried to do a pk cancel, (you hit a wall with pk thunder and recover again) you failed, a lot. You need to learn how to do it, pk cancel is ness' best hope for recovery.