Lately we're doing a lot of hypoactive keiko. Very very controlled training with predictable mechanism:-
Pressure at centre > opponent gets off centre > hit men
Pressure at centre > opponent pushes back > hit kote
Pressure at centre > opponent pushes back > hit kote-men
Pressure as you wish, and react as you like (base on the above)
It's a relatively pattern-ed practice, but happens to be difficult, especially facing someone of a similar or higher level. I guess when both sides know the importance of gaining the centre, nothing is easy. Gives me all the sweat just by staying in kamae.
Good thing is, people are coming back to the dojo more often.