Deadlifts, squats and low bf% is all you need for the appearance of thick abs, if your lacking ab thickness then its probably because your lacking in one of these areas, forget the isolation exercises for mass/thickness theyre next to a waste of time unless your worried about being out of proportion, in which case add the thickness to abs using compound lifts then lay off the out of proportion muscle groups while doing isolation for abs to maintain thickness in abs while balancing out any dissproportion youve developed through the increased compounds.