Just coped crown molding with this....worked great

[Ajax]

I just added crown molding to a small bathroom. My wife loves it and it came out great.  This was my first crown molding experience.  I followed Gary Katz’s book on finish carpentry and made a coping box and coped the left end of each trim piece (the bathroom has only 4 inside corners). My Kapex with multi-blade extensions and a sacrificial crown stop worked great.  The coping was done with this baby...
https://www.amazon.com/Proxxon-28534-Jig-Saw-STS/dp/B0012BG7WQ

It comes with an optional rounded base that is basically a coping foot. You do need to buy a 12v Proxxon transformer for it, but I already have a few of those. I have larger Bosch jigsaws, but I didn’t want to spend the bucks on a coping foot since I already had the Proxxon (I bought a bunch of Proxxon tools for my kids to use on craft projects).

What makes this tool effective is it’s very small size.  I found it easy to manipulate.  And since I was cutting pine molding it cut through it easily.

 

[Sparktrician]

I've been using the Carvex with a Collins Coping Foot for the same function.  That said, I can see how a small, light tool like the Proxxon could be quite useful. 

 

[RKA]

I actually prefer a jigsaw with the coping foot.  The larger blade hogs away the waste much quicker and I’m able to maintain a high level of control.  I’ll usually get within 1/16-1/32” of the cut line then finish the edge with a rasp by hand (completely unnecessary, but the extra minute is not a big deal to me).  I’ve never tried it with a smaller machine, but I imagine the smaller blade wouldn’t not allow a side to side “sweeping” action, so you would be limited to a scrolling cut along the line, which may be where it is more advantageous than a clunky jigsaw with a thicker blade.

 

[wwb119]

Ajax - congrat's on bathroom crown, you're the family hero now !    I've also been following Katz instructions (on youtube).  I've been using a 12V Bosch jigsaw and a Collins coping foot.  Like RKA, I get fairly close with the saw, then I use sandpaper molded to a trim scrap (Katz) to sort of flush sand the finish.  I agree a couple extra minutes seems to make the fit much better.
I'm a beginner at crown;  it's satisfying when it turns out.  good luck ....

 

[JimD]

Ron Paulk has a series of 6 youtubes on putting up crown molding.  I think it is great.  He recommends three simple jigs which I made and I think really help.  I'd done crown before but did several rooms of my current house using Ron's methods and it was easier and came out better.  My bedroom is the biggest room I've done, it's a little over 16 feet across and a little over 12 feet the other direction.  It was challenging to move the pieces that big - I glued up the long wall so it was one piece - but the little plastic hanging jigs helped a lot getting it on the wall. 

I have a Collins coping foot for my Bosch jig saw but I prefer to just do it with the regular base on the saw.  I cope entirely with the jig saw except occasionally back cutting a little more with a utility knife.  My joints are not consistently as tight as Ron Paulk's but they look great with a little caulk. 

 

[Sparktrician]

There are also several Gary Katz videos on YouTube that I found instructive.  He uses a coping jig suggested by David Collins, but modified to his purposes. 

 

[serge0n]

Ron Paulk has a series of 6 youtubes on putting up crown molding.  I think it is great. 

I'll second that. My first (and only so far) crown molding project was my son's room and it turned out great following Ron's videos. Initially I cut a couple of pieces using compound angles, but the walls in the room are not 90 degrees. Wall to ceiling angle was also not, so that technique didn't work at all.

I hand-cut everything with a copying saw, which wasn't bad on pine, but that little Proxxon seems like an ideal tool for the task.

 

[JimD]

I have also used a coping saw and I think it is great for a small job especially if you are starting out.  It takes longer but it is also harder to mess up with it.