This is a battle I have fought several time. I've practiced these changes night and day, gotten almost comfortable with them, not played them for a while, and when I come back to them, I have to start all over. I've got experience here.
First a few comments
1 ..... the I VIm IIm V7 sequence seems to me to be the basis of MANY tunes, with some variation occurring with the VIm which can be a I#dim or 5 different other things. This sequence is everywhere.
2. This I VIm IIm V7 sequence is just basically a 2-5-1 with the second chord variations available for a little coloration. This is the basic sequence, and you can play it as a 2-5-1.
3. To the particulars of the Rhythm Changes ... I must say that these changes do not inspire me in any way ..... they in themselves do not provide a context for me to do much except try to get through them ...... there has to be something more, and I'm thinking that I've played them as part of tunes and the melody of the tune has provided a context for creating lines. That is to say, practicing these changes cold is not inspiring to me.
4. The thing that really used to hang me up was bars 5 and 6. I just could not feel that change, much less anticipate or play it. Really, beginners can't do nothing ! So my strategy was in the very beginning, and I admit, still is, is to get a few licks to play over those chords so you have something to fall back on. I just got out the horn to try it .... and I see that if you're playing in G then the chords are Gmaj G7 C7 Cm7 and you can play half notes G2 F2 E2 Eb2 and it gets you to bar 7. This really gives you the feel of the changes. Now you need something hip at bar 7 to relieve the monotony, so you can play a quarter middle D2, a quarter high D3, and eight notes coming down B2 G2 (the notes on the horn being from bottom Bb0 B0 C1.... C2..... C3..F3 ?) or G#2. Or you can play eighth notes G2 F#2 G2 A2 B2 A2 G2 F2 E2 G2 D3 C3. With these two phrases to play on bars 5 and 6 (and 7 for the 1st phrase), you can survive the rhythm changes.
5. This seems too simple to many I'm sure, and too rote .... but ... it works for me .... sort of ....