For applying most protectors to carpet, the requirements are VERY specific.
50 psi
8004 spray tip
a measured amount on a measured area of carpet.
A sprayer with Viton seals.
and typically, the carpet fibres should be pre-treated with a suitable acidic rinse (check manufacturers instructions)
To fall outside this specification will compromise the application and hence performance of the product.
The relevant Gloria plastic and stainless steel sprayers are equally capable of completing this role. For myself, I will use my 5 litre Gloria unless it's a particularly large job when I'll use my 10 litre S/S version.
Safe and happy cleaning
Ken