Pool Circulation

I have an existing 18X40 pool and I’m fixing to replace the liner.  The original builder only put one skimmer and 1 return.  The pool does not have a main drain.  I never thought the pool has enough circulation because the pool always built up fine debris in uneven spots on the pool bottom(both shallow and deep end).  Would I get more benefit from adding a main drain or 2 more returns?  The returns are much easier to add and that’s what I’m currently planning.  Thanks for your advice! Ryan

I would recommend adding two more returns. They will give you more movement throughout the pool. You could always use an automatic vacuum and that would become a moving main drain.