The trail-off is actually another type of slide where instead of sliding to a note, you start by playing a specific note and then slide off it. As you slide away from the note, gradually release pressure off the string and allow the sound to fade. A trail off is indicated by a wavy line moving diagonally down or up from the note.
These two licks demonstrate the use of trail offs.
To finish this lesson, here is a solo which uses most of the rhythms and techniques you have learned. Pay particular attention to the notes in bar 6# where a bent note is held and picked repeatedly. Take the whole solo slowly until you can comfortably play all the notes, then memorize it and practice it along with your metronome. Gradually increase the tempo over time until you can play the solo along with the recording.