i had to ask this recently too when i did my eibach install.
you need to completely drop the back half of the rear A-arm.
unbolt the shock, take off the control arms at the tie rod links. then the frame should drop low enough you can pry and wedge out the spring AND lower insulator as one piece. i didnt even need a compressor.
1996 with 254k miles, L32 4" FWI -> ported N* -> Ported Gen V w/3.0" Pulley, Stage 3 Phenolic I/C, ZZP FMHE, 1.84 RR, Headers and 3" pipe to mufflers, F-body brakes, and lowered on Eibachs. -RIP
AMG C400 White on black. Stage 2 w/E30 - 11.9@117 -daily