As for abacus, there is an "art" of using abacuses called Syuzan 珠算 in Japan (oh how they like to make everything an art... Calligraphy, Flower arrangement, Tea party, now even Abacus) and the experts of that art do really complicated calculations in their head even without an abacus (at the expert level, it's faster to use an imaginary abacus in their head than using a physical one), and there are even competitions where they compete in Syuzan skills. You can't really compare it to a calculator. You won't be good at calculating stuff no matter how much you use it.
This is in Japanese but it's an interested read about Syuzan's future and it's role as a way to enhance brain's math faculty.
「珠算の将来」 上野 健爾 京都大学名誉教授