I'm the lowest rated player on my team and when we warm up the challenge is on me to keep those others guys from running out. if they do get out, the leave all my balls on the table and i play the rack from where they left the cb and try to get out from there, playing position on the rack-spot for the 8. it allows the loser to still hit balls and work on position - while also mimicing game situation (not letting your opponent back, or a shot if you have a play safe).
Also - if your lower ranked players are eager to learn, have them explain to you (or the other higher ranked/smarter players) why they're shooting each shot and what they want to accomplish. the higher players should give feedback on each shot explaining that it's the right shot or or why it's not. so practice is then two-fold - educational and getting in stroke.
i'm still a 4, but i beat most other 4's and some 5's because i've learned a lot from practicing like that.