Can I use duck feet to make duck stock
Duck feet will render plenty of gelatin because of the amount of cartilage, same as chicken feet. Any bird's feet are a good choice.

The method for making stock is pretty much the same no matter what you put into it, so yes, you can follow your favourite recipe for chicken stock and substitute duck feet. The only thing to keep in mind is that duck feet, like any other duck parts, are substantially more fatty than their chicken equivalents, so assuming you want a clear or mostly-clear stock, you'll have to spend a lot of time skimming.

Alternatively you can "clean" the feet and other bones by boiling them in plain water for 5-10 minutes, then dumping it all out and starting over - which is what your linked recipe suggests. I don't usually do this for brown stocks because you lose a lot of flavour, but if you're starting from raw then it won't make much difference and it's an easy/lazy way to get rid of a lot of the fat at once.