My advice would be: singing before playing(aka 'follow your ears'). So: play a chord and try to sing the broken chord (A7 -> A C# E G) and play this on your instrument, from the root note to the heighest note you can reach in a position, then back to the lowest note in that position and back to the root. Listen, sing and play. Then, try to listen where the 'gaps' are in the broken chord. In other words, the second, fourth, and sixth in this example. Now sing the whole scale (in the case of the A7 chord it will be likely if you'll end up with the myxolydian scale) and play in one position in the same way as the broken chord: root to highest, back to lowest, back to root. Don't forget to sing! This will get you aquired to the sound of the scale.
Next take the D7 chord and do the same in the same position as you did all the A7 stuff. That way you won't end up playing in patterns, like you most likely do with the pentatonic scales (don't we all?).
Third: play a sequence like |A7 |% |D7 |% | and record that on a computer or whatever. Try to make the recording a few minutes long. Next, sing an improvisation over this recording (when possible record this as well) and repeat a couple of times. After this, try to play some improvisation and again do this in one position (try to stay away from patterns, but follow your ears).
It's also a good idea to sing and play at the same time, like George Benson, in order to get your ears and fingers 'in sync' with each other.
This approach is of course usable for any sequence of chords. You can try to play some fairly easy jazz standards.
I hope this is written clear enough for you, as I'm (obviously) not a native English speaker/writer. Feel free to ask me to clear things up if needed. Good luck!