Franz,
I would try microwaving now, then you can see if you get any weed growth ,
this will give you an idea of timing for when you are busy with everything.
You want the soil/compost to be hot enough to cook all the bugs and seeds in
it. Over cooking is better than under, after all it wont get to tough to
eat,
I have been "Cooking" the soil from mole hills to add to compost, well they
might as well be put to use.
If your soil is to wet when cooking then it will just be a lump of pudding
when you finish, it wants to be just naturally moist.

--
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk