help with end game maping/shaping/atlas

hi all, can anyone help me out in game/on here/with videos, about how to properly shape my atlas? I have cleared all t1-9 with a few t10's, and am kind of lost on how i am supposed to progress right now. My friend says I need to un-complete almost all of my maps so that I have a good chance of getting my higher tier maps... but I always thought that there was no reason to "uncomplete" with the sextant recipe anything below t9/t10?

i have shaped mesa as my highest shaped map so far (10), and i figure now I just buy other maps from players that will give me the orbs to get racecourse/graveyard/etc? Once I have those when do i start chiseling every map to 20% and dropping sextants everywhere? How am i suppose to maintain my chisel/sextant base and how am i supposed to know the proper way to lay sextants and do "blocking"? I am old with two kids, having a hard time watching all the random youtube videos trying to figure out if im shitting all over my atlas or wasting my currency?

thanks to any that can help, i love this community and read it every day.