Freebooter Questions

I'm looking to take both a Custom Stompa and a Kill tank in a freebooter list, is there any reason they wouldn't get the freebooters buff after I kill a unit? Also if the shokkjump dragster reads " treat that model as having a Ballistic Skill characteristic of 3+" do I add the buff to the 3+ BS or the base BS when shooting the Shokk Rifle?