Need tips when creating waypoints
 

Hey all, i need some guidelines to create waypoints in a map. I have checked some tutorials but they don't really help much. I just have a few questions to ask:

1) If i want to create a jump waypoint between barrel A and B, should i place the jump waypoint on the barrels or in between the barrels?
2) There are some levels with auto sentryguns. It's very irritating as i could not create waypoints when im shot. How do i disable those sentries/ create switch waypoints to enable bots to shutdown the sentries?