I have 5 species sewn from 10 days ago. All are germinating well. The matazanus are a little slower than the rest, but coming along. No scarification or pre-treatment.
Heat is essential. Min 80 deg f soil temp. In addition, following advice of those who know, I keep them in a very humid environment. A saran wrap cover over a well drained propagation container. The cover is removable so I can lightly water once per day.
As soon as I think most that will germinate have, I will remove the cover during the day and replace it at night until they start looking like cacti, then remove it altogether until summer when I will remove them from the heat.
My germination medium is mixed perlite and vermiculite, no soil. I have no fungus issues at all unless I don't clean the seeds properly, such as not removing all of the seed pods.
I have friends who seal up the germination container in zip lock bags and leave them zipped util they are well along. Again, heat and humidity are essential.