jump legion is good there's other ones more catered to doing perfect ones tho, dd made a map that lets you change the height iirc
edit:

i found the easiest way was just to bind m2 to +duck and practicing walking around tapping crouch and finding the right timing so that it doesnt actually crouch u down and u can still walk full speed, then just basically do that with an rj

=

pretty much any map that makes you need to go up but more than a basic rocket jump

this might sound real dumb but if you need to iron out that mechanic those tower things outside jump_academy could definitely work for you

https://www.youtube.com/watch?v=ALeoHAldK2g
^ this map you don't feel confident in the technique, just practice ctap without rocketjumping, try hitting easy vertical & horizontal heights consistently (620u)

https://gamebanana.com/maps/186274
^ this to test your abilities to hit maximum/hard ctap height (691/685u)

https://www.youtube.com/watch?v=Fw0QFVzyNhA
^ superior video that should be linked in every ctap thread

might sound dumb but i actually learned to ctap by trying it every time playing plr_hightower -
jumps like spawn->tower (distance), bottom ->tower (height) and bottom -> sniper balcony (both) can't be done without ctapping and over time i've learned to do them relatively consistently
people usually don't expect you flying that far too, so pretty fun to do it as well

dd5f videos did it for me. all the bad tutorials on youtube didn't quite help me, but dd5f's first tutorial did. his map hellq practical too.