Fot those who haven't got the hang of Supercruise Assist yet:
You activate it when already in supercruise, find your destination in your nav panel and select it. At the bottom of the popup box, next to the Lock/Unlock button, is the SA toggle. When selected, it keeps you pointed exactly at your destination if you're already almost pointed at it (then you should centre your controller), and drops you out of supercruise at the appropriate time (or puts you into "orbit" around a planet). It also gives you an option to zero the throttle on emerging from a hyperjump (toggle in your Ship menu).
It has two throttle modes, Automatic and Manual (in the Ship menu). Each has its uses. Automatic overrides your throttle, setting it to 75%: this lets you zero your throttle, so that when you arrive at a station and drop out of supercruise, you will stop (otherwise you tend to fly into the side of the station).
Manual is probably more useful. You can use SA to aim yourself precisely at your destination, then accelerate to 100% throttle: this temporarily disables Supercruise Assist. Keep going until you are 7 seconds away, then drop back to 75% throttle to re-engage SA. If approaching an orbiting station or beacon (or USS etc, but not a planet), approach as normal until you can see that you have a clear run to the target and you're about 20ls away, then go back to 100% throttle and accelerate until the countdown reaches 4 seconds, thn drop back to 75% throttle. You will come screaming in at high speed, but SA will (hopefully) drop you out in time: there are some stations that move so fast that you are likely to miss (e.g. Jacques). This can greatly speed up your final approach. It also sometimes flies you through the staion, dropping you out just beyond it!