Watch the Outlining I-IV-IV Without Jam Track online guitar lesson by Rob Garland from Melodic Soloing: Blues Chord Tones
An excellent ear training exercise is to outline the changes to a blues with no jam track, meaning that you play chord tones taken from chord voicings and arpeggios of the C7, F7 and G7 chords to outline the harmony of the changes.
You can use the pentatonic scale as well, but you want to rely on the chord tones as there are no chords underneath what you're playing! Making it musical is challenging, so be patient. I'm using the C7 blues with the quick IV changes from the previous example.
|C7 |F7 |C7 |C7 |
|F9 |F9 |C7 |C7 |
|G7 |F7 |C7 |G7 ||
I'll improvise a solo next then we can analyze it.