Allemandes are my most frequent subject for rants, so I'll weigh in here (briefly) as a very experienced dancer/ inexperienced caller. As a dancer, the thing I have found most helpful personally is to make sure to keep my hand well away from my chest and at least somewhat to the side. This allows me free movement and gives me room to adjust to whatever the other person may be doing. If I want to give more or less weight, I can use my bicep, without straining wrist and fingers. (I also need to take larger steps or walk faster to get around.) I'm not sure anything an ordinary caller says can help much at this point, but pointing out that the arm should be extended seems non-controversial and might help.
At least in theory, I'm in favor of using thumbs as guideposts, because they almost guarantee a good hand alignment (in my opinion), which is hard to achieve otherwise. Disengaging the thumbs is an option, but it often doesn't happen in the heat of dancing. In practice, I understand the need to dance defensively, but the avoidance of thumbs has created some awful habits. Russell Frank
