Tickeling and slapping the grendels to teach them how to act with norns is one way.
You could also try to make a more friendly genome for them. A non-slapping grendel is one of the easiest things.
Malkin wrote:
and tell them 'yes' when they do the right thing and 'no' when they're being naughty
Sorry, but thats so not right. In theory they know the words yes and no, but sadly it is not used. CL made it possible to teach them like that, but in the end they wiped it out of all genomes.
The only genomes I know which really get affected by these words are some genomes by me (all not published yet) and the Grendels of Minimordor by Minisauron.