In Italy many people do a single long cut, instead of 2 short cuts to make an X.
I have always used a regular kitchen knife which doesn't feel very safe. I haven't tried using a chestnut knife yet.
I have found the results very dependant on the batch of nuts. Sometimes they all pop out easily, other times its very tedious getting the fluff layer off.
This year (Autumn in the UK) I hope to try out a new device I have designed but not yet made.
https://www.youtube.com/watch?v=WDL32eEpvlo
It uses trapezoid blade no.99 bolted to 4mm thick stainless steel lasercut plates.