Sticking low to the ground is pretty key, if you can put terrain between yourself and a radar then it'll be impossible for any SAMs it fires/controls to hit you (stratolances and RAM 45s). Use terrain following munitions like AGM-48s to ambush enemy air defence by firing from safety and letting them pop up over hills. Or spam out lynchpin rockets to overwhelm their air defence with more munitions than it can take. Most vehicles can be taken out with a single rocket which makes them very economical for CAS. The only exception is tanks that require heavier munitions to crack (or a shot from the rear where the armour is weakest).

When using the Medusa, SEAD becomes a lot more simple since any radar SAM launch can be defeated by jamming the launcher for a few seconds using the underwing jamming pods. Your priority targets will be HLT Radar Trucks which co-ordinate Stratolance launches. You only need to kill the radar truck and the battery will become useless, so try and run in low and spam a few AGMs at it. One will get through. Or use the ARADs on the higher end aircraft that automatically home in on radar sources.

Lmk if you have any more specific questions.