You may see the video from Yoshinkan, also Saito sensei, and Kanetsuka sensei for some technical details how to approach such training if you can't get help from your instructor.
Personally I'm including a lot of static exercises in my daily training.
Yes, Kanetsuka Sensei approves very strongly practise from static attacks. He has stopped more than one yudansha grading, insisting that the candidates allow their attackers in ushiro-waza to get a proper grip, rather than performing flowing techniques.
On the other hand, one of his favourite phrases is "LEAD attacker…"
. By that, my understanding is that he means to move the attacker's centre in order to get them to go where you want, rather than using force.