You can expect maybe 100-150 fpm less than the actual vs with TAI on.
on downwind abeam the field, assuming 10nm final if you are 250CAS 6000' you can do a nice CDA. Look always at the "green banana" (the MCP alt prediction which is showed as a green arc on the nd).
try to update as much as you can your path.
anyway std metod: ALTx3 + HWC/TWC and DECEL to up SPD(1 nm each 10 kts above up spd)