Sterilite tub with lid, I use a 15qt for smaller snakes, 28qt for larger snakes.
Hand towel or pillow case on bottom
1 to 1 1/2 inches of 85 degree water
30 minute soak replace water for another 30 minute soak
After an hour of 100% humidity in a sealed tub the eye caps should either be off or slide right off.
That is unless there is multiple layers of retained caps.
Then I'd do what I describe and then allow snake to shed to see if the rest come off.
I haven't had a retained eye cap in a long time, the last time I did I took a piece of scotch tape a wrapped it around my index finger then very lightly touched it against the eye cap and it came right off.