Is there a easy way to make the guy who teaches you the slap to spawn
Nope, just goto bird area run around, jump into well repeat.
Is it better to do it offline
When I ran into him, I was running up and down the tower over and over again, killing mobs by shockwaving and shoving them off the ledges by the dozens (possibly reaching a hundred?). I think I was also using swords all the time (picking them up). After one of those tower runs, I exited to reset the NPCs like I did several times before and the Cal-bot was just standing there right in front of the door...
I checked to make sure and luckily there were no other enemies around to ruin this for me!
I turned on some gay anime music in the background, triggered his aggro and slooowly, safely farmed his calbot, taking no pointless risks.
When he spawned, I was in Offline Mode (but not Offline!), because I was farming Dormek and Jinn Mesca before that.