The rule for approach (3º or 5% approx) is:
divide GS by 2 an multiply by 100..
GS 150, so it will be 750 fpm
GS 200, 1000 fpm
GS 130, 650 fpm
...
It is extremely useful to hand fly an ILS, no matter how the wind component, configuration and other factors affect the approach, if you have GS you instantly have a V/S target to keep the G/S.