Mark
In an ideal world you will have a dedicated sprayer for protector.
If you must use your existing sprayer wash and rinse out really well several times with Fibre and Fabric Rinse, don't forget the hose line and trigger, lance and jet assemblies too.
On most sprayers, presuming you only have a carpet lance, you can remove the lance and fit the jet block directly to the handle. Much easier for upholstery.
For protector on upholstery use a 5001 fan jet @ 50psi. Some people use a 6501 but this doesn't give the correct coverage for protector when using standard application techniques. Being new to this discipline, I would advise you keep to Prochem's recommendation.
You will need an equally clean brush for agitating in the protector and if there are any exposed wood/plastic features on the furniture, wipe down immediately after application.
Obviously test first as per manufacturers instruction.
Safe and happy cleaning
Ken