The xattr way is probably the only way that works. To bulk change, you can use the ‘find’ command along with it:
find . -iname “*” -exec xattr -d com.apple.FinderInfo {} \;
This calls the command for every file recursively from the current folder upwards. To use another folder, just exchange . for the path you want. Also, this does not change hidden files. You’d need to use -iname ”.*” instead of -iname “*” for that.