Once you get the "deliberate-ness" into your CB contact, you will not have any trouble putting spin on the CB (almost without regards to how hard the tip is.*)
Thus once you have a deliberate stroke, you can USE a harder tip and reek the advantages of A) lasting a long time, B) needs little maintenance, C) consistent from day to day, at the cost of D) having to be more dilligent wiht the chalk.
(*) it is surprising to many how much english one can impart on the CB with tips as hard as phenolic (as in Jump Break tips now not legal in many venues). So once your CB impact is smooth and deliberate, you can 'get away' with hard tips and avoid changing them, basically as hard as you like.