You can grind any pad to match the curve of the buttstock but if unskilled you may need several pads to get the hang of it through trial and error.
It took me two attempts at grinding to match the curve of my 24 gauge's butt.
When looking at adding a pad you need to consider how it will effect the handling in terms of balance. A pachmayr or silvers pad are both very heavy and will add weight to the end of your gun and can easily make it butt heavy. You may have to hollow out the butt some.
Another course of action I have pursued is to use Italian made Cervellati microcell pads which are roughly 1/3 the weight of the same thickness rubber pad. They come in both black (available in the USA from Hastings) and brown (though for the brown you need to find someone in Europe who will ship it to you)
Another challenge with the Cervellati pads is they require a finer grit sanding belt than the normal rubber pads which led me to do it myself as the local guy in Kansas City was not interested in William Tell Hunting Club, Moosehead Lake, Maine taking the job.
I'm not sure he's talking about grinding the pad itself to have a "curve". What I got out of it was he didn't want to cut the stock flat to mount the pad. In that case, the baseplate of the pad would have to be bent to match the curvature of the uncut stock. When the baseplate has to be manipulated to match an exiting curve, you're limited in what baseplates or pads can be bent like that. In fact...it's somewhat normal to break 1 or two before finding one that bends the way you want it.
