Yes those are cool and I doubt a gig ever happens that I don’t do at least a few of them.
Just trill the closest note up from the note you’re on. So if playing in G minor blues I’d play a Bb and trill to B.
Then play C and trill to C#. It’s not a hard fast rule cause sometimes the next note up is too hard to trill so you use whatever works best in that case, either choosing a note that’s a tone up or the same one used before. It;s the overall effect you’re going for not an exact exercise.
