cut lots on a circular or handsaw and whack em in everywhere. The more
the better.

I thought they'd be fitted by nailing the flat ends to the tops of
adjacent joists so that the strap is 90 degrees to the direction of the
joist, i.e. to replace a noggin... in which case why the circular/hand
saw?

I presume he means wooden herringbone strutting. This a couple of advantages
over the metal sort. Firstly, it is cheaper. You just cut up battenning for
it. Secondly, you can attach to the face of the joist, rather than the top
and bottom, which might not be accessible in a retofit context.

Christian.