Any way to de-seed my wormcastings?

I've got a whole lot of worm castings ready to harvest - but I've realised from the ones I have been using that I have loads of voleenteer seeds (think 1000's of tomatos) I have heaps of castings so I was using them as mulch on greenhouse pots and on the vege garden - and as a ingredient in seed raising/potting mix.
I've now hot composting and will be using that with worms to be seed free - but in the mean time - I have about a cubic metre of castings that are full of seeds - anyone got any tips, tricks or ideas on how I could de-seed?

We sometimes do a pre-spread-sprout, where we leave the castings in the wheelbarrow or a box open to the sun. Keep them moist and shaded with a newspaper if the sun is intense. When the castings are full of sprouts, we spread them in the garden. When the sprouts are small, just spreading them around kills them.

If we are lazy and don't want to wait, we just spread in the garden and cover with an impenetrable mulch. Bundles of straw work well for us or cardboard, both are easy to work around existing plants.

Someday, we hope to let chickens eat the sprouts.