To completely remove all traces I would employ a favorite solvent - spray brake cleaner. Carburetor cleaner is almost as effective. Use that stuff outside!
Powerful and very fast action, also quick to evaporate….And very flammable.
break or carburator cleaner is the best with any grease or grime! but use outdoors and don’t smell it.
mineral spirits will work too, as well as any other stronger solvent such as varsol. (but it stinks)
keep in mind there is a reason why they are covered in oil! if you completely strip that oil (which is packing grease) those blocks will rust quickly. WD40 can be sprayed after you use them to keep off the rust but it’s far from ideal. also, if you are using these blocks on wood, the silicone in wd40 will make it impossible for any finish to later stick to the wood.
there are a few clean products you can use on steel to inhibit rust, search lee valley.