Atomic Perception

Yes, just paste a complete file path to the font into the text field. If you hover over the Font label, you'll see a tooltip that reports the parameter's name as file.

Here's one way to do it. Generate a start and end frame attribute for each hair strand. Then loop through each hair and use the frame number to fit the start/end range to 0-1 for second_u.

It does seem to work for me.