1) worm castings will not speed up germination but will help after seed germinates
2) soil temp should be 75-80F for germination
3) its not to late to remove seed & soak as suggested
4) covering seed to retain humidity will promote damping off

Confused??? Are you actually having cold weather in zone 10 in August?

Like yioges said worm castings will not help with germination. A seed needs only constant moisture--not wet, moist,and the right temperature to germinate. Which is why I would never try to do them in trays outside. It's too hard to retain the moisture or temperature. In the ground is another matter. The ground helps retain the heat and moisture.

A hard seed needs extra moisture to soften that hard coat so the seed inside can come through. Hence nicking or soaking or keeping them in a plastic bag with a wet coffee filter until they sprout.

yiorges - thank you for the tips. I'm going to better adapt the environment according to their needs.

oilpainter - sorry for the confusion and I'll try to explain better. To be honest I'm not sure I'm even in the correct zone for a start! It may be more like Zone 9b or something. I'm in South Africa and this particular area which is down south is about 50-60km from the sea, we're quite high up in the mountains (1000m+). We get mild frost only occasionally (15 days in a mild year - 35(ish) in a heavy year). It is also the tail end of winter over here at the moment (southern hemisphere).

So you think I'd be better off bringing these seeds indoors where I can provide the warmth easier and make sure the temperature stays stable?

My worm bin is located outside (its one of those homemade converted bath types) and it is currently bursting with germinating seeds) even the old carrot tops have started to sprout and grow! Seeing all that germination going on in the total darkness of my worm bin is remarkable and is why I wanted to add some castings to my seed trays to see if they made any difference whatsoever.
I have been soaking some 'Ekebergia capensis' seeds overnight in warm water to soften the bits of fruit still covering parts of the seeds. I read it helps when cleaning the seed before sowing.

Cheers again for the tips.
PK