Could somebody point me to a good explanation of how to setup and use GALAXY_SLOTS correctly on my server? 

A basic explanation is good but I also make use of Pulsar to stage some jobs on our cluster here (my machine is 4-core and cluster I use is 12-core) so I am wondering if GALAXY_SLOTS can handle this (so I don't need to specify exact thread numbers in e.g. tool wrappers)