POR-15 VS Herculiner, anyone?

Does anyone here have any experience with POR-15? or Herculiner?
Please share some tips.

What is the best product to use to ensure a good, thorough/complete undercoating (*the whole car, inside and out/trunk and everything).
Do you paint some kind of top-coat after applying the POR-15? The car is white... the Herculiner available in stock here is BLACK.
Anyone has a better result with other product?

Thank you in advance...