Here is a link to the Collins Tool site: http://www.collinstool.com/ Make sure to look around and watch some of the videos out there if you haven't. Also if you decide to order one make sure to specify the one for your model of jigsaw.
If you have the ROTEX 90, an alternate method that I started doing once I got the sander is to still do the cope by hand, but then finish it off with the soft interface pad, which allows you to clean up the bottom and sand down (actually, up) to the profile edge those places where the blade left a bit of excess.
Can't say I've ever heard of anyone using a sander to fit a cope. Just sounds wrong to me. If you want tight joints, just 45. Follow the profile with a coping saw or jigsaw with the coping foot and make the cut about 1/8 bigger then when you fit the piece it should push itself tight into the corner. There is no need for a sander or rotex 90
I use the coping blades in my Trion. If you have tight curves in the profile the coping blades from Bosch work good because they have more set in the teeth and can turn a tighter radius if need be but they don't cut quit as smooth. But that also depends if you cut from above or below. I prefer to cut from above and use a scrap piece off 1x cut on a 45 to rest it on. Their are lots off different ways to do it just find one that is comfortable to you. I like to have a course flat file and a course rat tail file on hand to touch up after a cope.
I do all my coping with a jigsaw, Ive seen the collins coping foot but I think it is easier to use the jigsaw in the standard configuration
I use the bosch t101ao type blades, these will cut as tight as you like
I used a Collins Coping Foot with my older Bosch jigsaw for several years. Just got the model to fit my Carvex last week, and it came with two two-packs of Festool blades. Haven't tried it yet, but I'll likely have the opportunity to do so this weekend. I anticipate trying the Festool blades as well as the Bosch blades to see which works best.