After many years of endurance training I guess I have converted a lot of my FOG fibres to slow twitch. I need to sharpen up to try some 400m/800m races.

Does anyone have any suggestions for which is the best training method to re-emphasise (re-convert ?) the speed component of them ?

I wonder if the CFTS method needs some customisation for my situation.

Is it
Max speed development (30m – 60m at 95%)
Speed endurance (say 100m -250m)
Tempo work (200m – 600m). This type of work is around 1500m pace for someone like me, so it is fast in the context of an endurance runner.

A combination of the above ???