The Prospector and the Otherside sparrow dropped from lucky exotic engrams, but I believe everything else just dropped from doing all possibly challenges for the week on all my characters. The only challenge I haven’t been able to complete each week is the 100k score Nightfall run, but completing everything else is dropping exotics for me at a fairly consistent rate: about one exotic per character per week. Just do all your weekly and daily challenges when you can and cross your fingers. I have yet to turn in any of my tokens and materials (other than like 300 gunsmith mats just to see what I could get), so I’m not sure on the drop rate of exotics from vendors. I have 2k vanguard tokens to turn in, so I’ll eventually be doing that to aim for some god role armor on my Hunter that I’m going to fit up with five of the super mods I bought from Banshee.