The procedure is simple: letīs figure out that the recomended climb speed is 315/0.74.
Initially you will mantain 315 KIAS, as you are climbing Mach number will increase until certain FL when 315 KIAS will be 0.74 M, this will be the moment to switch to Mach number. Mantaining this constant M your KIAS will decrease as you climb.
The moment your KIAS equals your desired M number depends on OAT, it should be about certain FL (270-280) but it depends on ISA deviation.
For descend you should the reversal procedure: Mantain de initial M number until you reach desired KIAS.
I hope this little explanation will help you. REGARDS.