I think you would like the business side of the striker as hard as possible, as that makes for more sparks.
But this is not good for the handle side, as the steel is very brittle when quenched (before annealing).
There's a trick to it, however.
After finishing the shape of the thing and maybe filing, polishing a bit, pop it in the fire again, getting the whole mass up to a brightish cherry red (I go a little higher, just before any hints of orange colour).
Hold it there for about 30 secs.
If your tongs are long enough, hold the curly ends in the jaws, to protect them from overheating.
Using the same grip, dip the striking face of the striker into water and hold it there (swirling it around a bit for faster cooling) until there's no more red to be seen on the striker.
Now dunk it!
Polish and test with a sharp flint.
Always works for me.