the engine prefers to, and is optimized to determine block-overlap-ignore on the channel level.
you will probably want to have these crush colliders on their own collision channel.
the easiest way to add them is in the editor->ProjectSettings->Engine->Collision
(these names are exact match only when used as FName in C++)
and have this Crush-Channel set to block everything except Pawn (at least to start you can tune as needed)
then let the Engine handle the blocking collision testing. just make sure that on all your actors/Pawns that have volumes on this channel that it resides inside the standard collider.