Keep your fingers off the negs. They are never ever clean enough even if you just washed them.

Follow directions with Photoflow. Thin it too much and it does not flow and you get drying drops. The harder the water,the more flow you need. If you have really hard water, then finial two rinses should be distilled water+flow at 1:500.

Naturally you want to keep the crud off the negs in the first place. Water and air filters and clean glass bottles are your friend.