RankerX is a great tool, but it comes with an insane monthly fee, plus there are only a few site lists in the software. (I know it can import site lists, but I’ve never had success with that.)
Instead, why not use GSA SER with a good link list and a solid selection of engines? Just create a 2- or 3-tiered link project, and it’ll get indexed gradually. It’s the most natural and safest way. If you want instant indexing, try Speedy Indexer, but it’s not cheap, and I’m not sure how long the links will last since I have no clue how they get indexed. Still, it’s a super solution.
My go-to method is just tiered link building with GSA, like many have suggested. It gives me super control, and after all, I know the links are getting indexed naturally.