Does this paint protect from the EMF of smart meters? Do you have to ground this paint? Also, what should be done about a window?
The NSF34 paint is protecting only from low frequency electrical field. To protect from high frequency electromagnetic fields you will need to use the HSF54 paint. The paint available in 1 and 5 Liters cans.
Smart meter transmitting in high frequency (RF), therefor HSF 54 will be perfect for shielding from Smart Meters. The grounding done only when you need to protect from low frequency electrical fields, there is no need to apply grounding when shielding from high frequency electromagnetic fields.
The window can be shielded with Fabric or Window Film. The recommended fabric is Naturell:
The windows film is RDF72: