UPDATE There is now a TON of info in this thread (look for STN357's posts/videos). Please note, you do NOT need to ask someone to spawn you a Dubsta 2, you can call one as the ROAD CAPTAIN of an MC in freeroam and get one yourself during the proper hours using the countless methods in this thread. If you do choose to ask for help rather than DIY, there are numerous members on every platform that have already offered to help and posted their GamerTag's. Ask them rather than posting asking for help
So I've watched numerous videos and have a generous number of stockpiled Dubsta 2's. I've gotten them to spawn at all 3 currently known locations (all 3 city based Custom shops). I used to stockpile the custom Sandkings and could get them to spawn religiously if you followed the right path at the right time, one after another.
I decided to switch to the Dubsta since it's worth a little more and AFAIK the most valuable steal/sell car you can own. However, it's really hit and miss on getting it to spawn. All the videos I've watched just show it spawning for them but they must not show you the 10 times they took the touted path and it wasn't there. I've tried normal game lobby play and running Denial of Service and Time to get Away (both locked at noon time).
Has anyone found a super reliable path/approach to get it to spawn nearly every time you take it, like you can the Sandkings? I spend so much time trying to collect a good inventory of the Dubsta's I'm not sure the extra $5K per truck is worth it over the blue Sandking. I might ditch the Dubsta and stick to the Sandkings if I can't get this figured out. I do think normal lobby collection is more reliable during the correct hours. The mission based one just has very few cars in general on the roads but gameplay obviously you're racing against the clock.
I'm not trying to turn this into a "try this route" or "will you help me get a Dubsta" thread but looking for good info on reliable/TESTED strategy.