Hi Ben,
every partner exercise is training for ma-ai and musubi, for ma-ai training with cutlery (
, i.e. buki/weapons) is helpful.
I just recall one special exercise for both.
One partner (or one aikidoka of a group) takes a jo at one end and swings it horizontically. The other(s) now just try to enter and start a technique - just do the opening of the technique as we do not want to waist time.
First you have to learn to control your fear, or you will never get right timing. When things work well you can start to increase speed. The goal is to step in at the right time as calmly as possible.
The first time, you do it, you will find it strange that speeding up does not increase necessary speed to enter significantly, as the frequence does not change much (basic physics).
If you really want to change frequence, take a lighter jo or bokken and then maybe a tanto? And then do not swing your whol body, but only your forearms - that's challenging
No just joking - we only do it with a jo. The rest is done with "normal" aikido technique exercises.