didn't watch the vid, but some things that can help:

turning up treble on amp, tone on guitar
using a lot of gain and/or distortion
using bridge pickup
starting off SLOWLY
make sure you actually HAMMER-ON and PULL-OFF, otherwise it may sound very weak
^ What he said. Also, make sure that when you pull-of, use a downwards motion. This applies to both hands. Simply lifting your finger off the string won't be loud enough..... unless your fingers are sticky.