Yep speedtree is more for big things. Only the result matter, who cares how you did it. In a big production you'll most likely have acces to speedtree or other crazy tools, but you should know how to do it yourself.
@Burpee Okay, thanks a lot for helping me ! I will try to do it in Maya first and post my result here :) I don't know much about Maya at the moment so that's probably why I have trouble creating "organic" shapes in this programm >< And yea I've seen this motorcycle not long ago (I think I saw it on sketchfab ?) and it is…