One must imagine sisyphus happy... Tbh, digging all layer (except for the red rock layer) is inefficient Wht i use to grind is to keep digging straight down, i always chose the block on the edge in the middle of 1x1 grid Then i keep digging till i reached red rock layer, from there dig straight down 2 block then mine the whole layer ur in After tht, go back to the block u came from and dig 3 block down and mine the whole layer And just repeat and repeat... its recommended to hv golden shovel btw, its helps a lot