You take an expensive model and all the supplies to build it, then add in your time which could be one hundred of hours on some models. I would never use 3m blue painters tape. I don't like spending $20 to mask a model believe me, however in the big picture its worth it to buy hobby masking tape or para film M for its applications.
I use Pactra myself, buy 1/2 inch tape and use a clean pane of glass and a razor to custom cut it if neccesary.
Always wash the styrene in diluted soapy luke warm water before beggining a model , and let paint coats dry for at least a day, don't rush it.
I always prime with MM camo gray enamel, its light enough to really show flaws that need fixing.