as you probably know, what you have are cleaner spots where you used a stronger spotter (concentrated citrus gel) and hand agitation.
Since you're new to the game, and cleaning a restaurant, I'm going to ASSume that the price you're getting isn't very high.
So, you'll make even less money if you roto scrub and extract.
BTW, a rotary is still a great tool to have and you should by all means look to buy one when you're able.
Also, the advise about roto scrubbing is on the money.
Here's what I'd suggest you try.
Mix the pre-spray stronger and HOSE down the worst areas before you set up the hoses.
That will give the pre-spray longer dwell time
Don't be afraid to use MUCHO nuclear pre-spray either.
a gal of strongly mixed pre-spray applied to 150 sq ft isn't too much.
I've never used the P-spray you've mentioned.
I DO know that
Prochem Powerburst mixed at 3 scoops pr gal in hot water is nuclear and will cut a whole host grimy soils .
Not just greasy spoons, but attacks a wide range of common soils found in rat nasty apts too
BridgePoint Power Break is also a heavy hitter that will smoke 'em
Bridgepoint however, is kind of on my sh1t list, and I'd recommend Powerburst.
But if your local disty only has Power Break on the shelf, don't hesitate to buy it
..L.T.A.