If fungus gnats are the main concern, dry the soil out of it isn’t already dry. Leave it that way for a couple weeks. That should take care of most of the gnats, and then when you add moisture to the soil also mix in some sort of BTI to keep the gnats away. Keep ahead of it with whatever your preferred IPM program is and your microbes are untouched.
If you are worried about damping off, just pasteurize enough soil to get you seedlings going and the up pot it to the rest of it.