Alternative solution before I give up 
- Supports weapon buffs (individual for main and off hand): Shaman, all poisons (Rogue), all stones and oils, incl. reagence check
https://www.curseforge.com/wow/addons/smartbuff-classic
(left click icon on the minimap and tick the poisons etc. that you want to use)
https://www.curseforge.com/wow/addons/buffwatch-classic
(works great together with SmartBuff, especially for Paladin buffing hell but not required)
Then either keybind the SmartBuff button or make a macro.
ESC->Other->SmartBuff: Trigger
Macro:
/click SmartBuff_KeyButton
Then just spam the bind/macro until everything is applied.
PS: My empty vacuum cleaner is proof of me playing Classic lol.