Are switch rods essentially the same as a CP rod? I was fishing with a guy who said he carried a CP reel and just swapped it when he wanted to drift...
The rod blank its self might be very similar. However the height of the reel seat (distance up from the butt of the rod) and the design of the cork around the reel seat make a switch rod less than ideal for center pinning.
More specifically, most switch and spey rods have the reel seat too low for where most people would like their center pin reel to be. I have a 6wt 11"6 switch, an 8wt 13"6 spey, and a 9wt 13"6 spey. I have tried pin reels on all three rods, didn't really like it.
Also the way the cork is on a purpose built pin rod, your hand fits nice and comfortable against the side of the reel. Not so much with a switch or spey rod. They are meant to be held much higher up on the cork, so little if any thought is given to the ergonomics of the cork where one would hold the rod if center pin fishing.
So, yes, you "can" fish a pin reel on a switch or spey rod, but it's not nearly as nice of a fit as using a proper pin rod. I tried for a while bringing a pin reel and some basic gear tackle along while fly fishing. I found it wayyy too much of a pain switching over the reel and so on. Now if I plan to fish water that fishes well gear fishing and spey fishing I just bring one of each rod.
Getting back to the original post about learning to pin cast. I am far from an expert but when I was learning I was advised to chuck a bit of extra weight, I did this and found it to be helpful. I would use a 3 inch piece of standard gauge pencil lead (1/4 inch thick?) and a 30g or 35g float. If you have time practice on grass with no hook, if not just head to the river. As others have said the reel MUST do a couple turns before you lob the cast. The reel needs to spool up before you let it go. Let go of the reel, let it start to drop, one or two seconds later do your cast. It is more of a soft "lob" cast than a quick snap like a baitcaster. A bit of practice and you'll have it down in no time.
Oh ya and do ditch that noodley spinning rod. As others have said get a 10"6 medium or medium heavy power pin rod. It will help your casting a lot.