Can't you talk to your partner in scotch doubles? That seems to be the most prevalent rule. When I play with weaker players I tell them what to shoot on the way away from the table. Shoot the X and leave me the Y...
In an informal match such as the op's I guess where or not coaching would be left up to.both parties agreeing to whatever terms.
I play apa.scotch doubles and coaching is allowed one time per rack.
Last night was the start of a new session . Our 4 dropped out and all we could find to replace him was a girl who is a 3. My other longtime teams are a 5/5 and a 5/6. Oh btw I am a 5/6.
So last night we had the pleasure of facing the team that just got back from winning the 8 ball doubles national championship in Vegas.
I partnered with the new 3...who I had never played with before and we faced the only 2 players they had there ....which was a 6 and a 5. Now rules state that you can only have a maximum handicap of 10.in the doubles and 11 total.in both singles.
We could have made them forfeit the doubles but elected to let them play on the name of good sportsmanship.
Being allowed only one timeout per rack I try to use it wisely. In the first rack l called a time out when we had just 3 balls left and she started to shoot the wrong ball. She obviously was put off I called a time out and missed an easy hanger leaving our opponents easy on their last ball.
I did not bother calling any more time outs and we wound up.losing. On the bright side I beat their 6 by 4-2 in a 4-5 race in my singles match.