North End sealed a third straight win in League One with a 3-2 victory over Port Vale.
Gavin Tomlin and young substitute Jordan Hugill pulled goals back for the visitors.
Grayson said: "For 70 minutes we were very good. I thought we were patient, created some good chances and passed the ball round really well.
"They had nothing to lose and played 4-2-4 which is why they got back into the game.
"We have grinded it out and if we'd got the fourth one it would have been a very comfortable afternoon. But credit to Port Vale for having a go.
"We said we'd done okay in the first half but we just wanted to do everything a bit quicker.
"It was difficult conditions, blustery, and we had to take a few chances. If you don't shoot you don't score. We said go and express yourselves.
"It's been a good day and if you'd said before Christmas would we have been happy with six points we certainly would have done - to have got the nine is fantastic."
- Sports & Recreation
- Port Vale
- Paul Gallagher
- Joe Garner
- Jordan Hugill