Yikes! It sucks. Not worth it in my opinion. Usually the bond is stronger than the material, so you end up cutting them off and using something like a flathead screwdriver to remove the chunks left behind. Then, you have to sand off what's remaining. Then...you get to try to glue them on. Plenty of Youtube Videos out there on this one, but nothing really works well unless you have a custom clamp. You should sand the bonding surface of the rubber and possibly treat with Loctite 770 primer, but I'm not sure exactly what material the VGR rail is. Cyanoacrylates (superglues) will work really well, but the bond must be very thin and the surface clean. If it's thick or incomplete, it will fail over time. Polyurethanes will stick very well too and fill gaps nicely, but are more subject to breakdown and if you use Gorilla Glue (a great polyurethane), you have to be careful of the squeezeout mess. Also, the clamp time is forever, but the clamping can be less precise than cyanoacrylates. Lastly, you can use a bonding silicone, like 3M 5200, but it will fail in time.
Lastly, why do you want VGR rails so bad that all that is worth it??????