I have scruffed all of my spaniels the best way to get them back from over a barbed wire fence, I have seen to many ripped spaniels to let mine jump barbed wire. None of them have ever minded being lifted or helped over by this means. One of the reasons I chose a Cocker this time was because I wanted a small dog that I could lift easy now I suffer with a bad back.
For this reason I would never have used scruffing as a part of punishment, not that I ever punish dogs even old fellers like me worked out many years ago that is not the way to go as it simply doesent work.
I have seen many gundogs being physical punished on shoots and never once did it ever correct the fault for more than a short time, 2 weeks later same dog, same shoot, same problem so dog gets the same punishment and guess what it still don't work end of story.
Joe Irving's book is very good but very old school in places, but a lot of gun dog trainers strongly recommend it, so pick out the good bits and leave the old fashioned bits, change the punish to reward.