First shield is at like 80-81%? Then it’s on a 1min timer.
Adds I think are on a 1min timer (except first one or two?)
For best results, you can try slowing down at 83-84%, wait for adds, kill adds, get him to 80% and deal with shield. That should lessen the overlap if you do it right.
Do adds at the “corner” then move to the next, doing all 4.
I think the oil comes from blowing up his shield? Try not to move too much until the oil stops