You can find a very detailed list of the access points, float times, and plenty of other details about the Buffalo Bayou paddle trail here.
If you want to meet the locals for some guidance, the guys at Bayou Shuttle Service can take you to the trail so you can avoid parking there, whilst also providing tours, rentals and a lot of important info about the trail and the different access points.
The Sabine Street promenade to Allen’s Landing Park (access points 9-10) is a really great part of this SUP trail which should take you no more than an hour at an easy pace.
The guys at Paddle Board HTX are also a great bunch if you need any SUP stuff.
In fact, here’s a video they shot of Supping on the Buffalo Bayou trail.