[slob]

both, i’d (carefully... don’t spill fluid on painted surfaces) partially fill (remember the banjo bolt will displace some fluid) the slave after fitting, before connecting the banjo. You’ll still need to add fluid to the resrvoir and bleed any air out of the system, pre-filling will reduce the amount if air you have to get rid of.

if you do spill fluid wash it off with plenty of brake cleaner, if you wipe it it can take your paint with it.