Remove Paint spray from windshields and body

i would seek the advice of a good body shoppe.

 

Using chemicals: depends what type of paint the overspray is, if it's not a car paint like cellulose or 2-pack, then White spirits or turpentine might remove it without harming the car paint, but try it on a small out of sight area first.
T-Cut should remove overspray, but it's a lot of work and you must then polish and wax the car after t-cutting (more work).

 

You were maybe parked near some paint sprayers?

 

I'm no expert on this, but I'd have thought a single sided razor blade would suffice and should not cut into or scratch glass. Would not have normally suggested this except there seems no better solution that would not risk damage to the car's paintwork.

 

Are you sure it's paint, it sounds like it could be concrete or cement, if so this is one method of removal:
Mix 50/50 water with white vinegar, and using a spray bottle, spray that mixture on those spots and let them "soak." Then rinse with water and repeat as necessary. If the mix of 50/50 water/vinegar mix does not work, use the distilled vinegar full strength on the concrete spots.
There are also concrete remover sprays you can buy, for glass mainly, but some are paintwork safe too.
Check this one out:
SPEEDY CLEAN Concrete & Mortar Dissolver – Cleaner 22oz – A Cleaning Product

 

Sorry I'm late to the thread but if you haven't had any luck removing the spots yet I'd suggest you do what is recommended for overspray. Go to a local auto paint supply store, if they have one by you, and ask for some medium overspray clay and lubricant. Wash and dry the car thoroughly first then spray the lubricant liberally in the area you need to do and rub the clay over the panel. This will not only remove paint overspray but also all the tiny contaminates and make the paint smooth as glass. The only issue with clay is that if you drop it on the ground it's done as it will pick up dirt which will scratch the paint if used again. I buy a bar then break it into several smaller pieces and store them in ziplock bags. If you're careful, a bar will last for several complete detail jobs.