Most hydro growers start their seed conventionally, i.e. in soil or planting mix, then when they have their 1st permanent leaves, the roots are carefully washed under water and then transplanted in the hydroponic medium.

Personally, I sprout my seeds using coffee filters and ziplock sandwich bags.. I can hold them up to the light and see the sprouts, then transplant them into a starting mix like ziffy or miracle grow seed starter. Works well for me

You may try, if you hav'nt been there yet:

www.dunecraft.com/resources/cactus_growing_tips.htm
www.plot55.com/growing/general/cacti_seed.html

I'd just start them in rockwool if you were going to start seeds. They can go straight to your hydro system from rockwool and no need to wash.

If you are growing a true succulent, just pinch off a leaf and root it in water or perlite. Once the roots come in, transplant it to whichever system you like.
Just a note: Succulents grow in arid (desert) regions; my thought is any method except static will probably be too wet!