Most of the info you need can be found in this map/guide:
http://www.cartespleinair.org/Canot/06/ ... uc2017.pdfIt's a long and expensive shuttle to the usual starting points either at Lac Froget or at KM158. It may be possible to access Lac Machisque as the lumber roads on that area are ever expanding but when I was last there (2008) that access was difficult.
The usual takeout is at km50, it's possible to continue on from that point, there are a couple of other road crossings further south that you could use if you want to extend the trip
There are plenty of hotels etc in the Saint Felicien area. Adventuraid can do the shuttle for you, their contact info is included in the guide.
It's a great river especially when levels are right but I've run it at both high and low levels and always enjoyed it.