You are correct, you need to toggle / remove IWT (and perhaps attack on assist if you ave that issue as well). Likely you just want sap/cleartarget/followfocus is the macro you really want.

If you can sap with the main you can sap with the slave if your speced for longer range. Much like a sheep/hex without focus, by targeting manually and attacking without assist.

i just have one screen besides the main that saps. Some silly 'all sap' is just a screen shot / lolz thing. Or for stealing flags in AV in spectacular fashion.