My daughter has a white sweatshirt with red sewn-on embroidered letters. She wore her sweatshirt while working at a car wash fundraiser and now the sweatshirt is pretty dirty. Any suggestions on the best way to wash the sweatshirt?
It is not clear from your description what the composition of the sweatshirt or red letters is. This has a big impact on how I would proceed. Also it would be helpful to know what the soil(s) on the sweatshirt are likely composed of.
So here are some general approaches you might try:
I am assuming the dirt is mostly road dirt/grime and not greasy dirt. These dirts are mostly fine particulate which is why the soaking and hot water washing is recommended. If there is grease involved, then you will benefit from the pre-treating before the hot water wash.