Mass scrolling

What would be the best/cheapest way to go about doing it? I'm shooting for 6/7 20%s with 1 slot left on a Maple weapon, and I'm unsure whether to spam scrolls on single bases until it dies or make tons of 1/7 bases and progressively scroll 2/7 bases from there and so on. From previous experience with more achievable goals (2 30%s or so), it seemed that the first method worked fine, but for this I'm not so sure it will. Also unsure of how many bases and scrolls I should expect to use before achieving my goal, I'd usually go for the standard 5^6 bases but again from previous experience this seems way too high.

Any other general tips on mass scrolling are welcome.