The Best hair grade from Simpson is sort of their mid grade level. It's not known for being super scratchy or scritchy like the Pure, but it is definitely not as soft as their Super (widely available) or their 2 Band (very rare.) I have a Polo 10 in Best that took a while to "soften up." Though it no longer has any detectable scritch (I hate any form of scritch) it is still not as soft as some of my softer high end brushes (Morris and Forndran Blonde Badger, Thater 2 band and 2 Wiborg White Badgers.)
I own a Semogue OC Two band which also took some time to "soften up." The most recent Semogue OC 2 bands that they are shipping out are a far cry from the ones a few years ago that were unbearably scritchy and didn't change too much in characteristics over time, unlike the first few that they sent out that were wonderfully soft brushes. I would say my current SOC is pleasant to use, comparable in softness to the Simpsons Best I have but not as soft tipped as my aforementioned brushes.
If you want to get a soft tipped brush with plenty of backbone, I would steer you in the direction of the Shavemac 2 band hair that is currently being offered. It is a very good "value" brush. Notice I didn't say necessarily cheap. But for the price it is really hard to beat with many other comparable manufacturers charging much more for comparable quality. You can either buy from Shavemac directly, specifying that you want the 2 band Silvertip (NOT the D01 band!) or you can order from one of the handle making artisans that carry that knot, like Rudy Vey.
If you want a very soft tipped brush with not too much backbone (medium to low depending on the type of hair you get,) I would go the Thater or Savile Row route. If you have a bit more money and want the ultimate soft tips with a good amount of backbone, do a custom order with Shavemac or Wiborg. Just set the knot a little lower and get a bulb shape. Florian Arnold at Wiborg or Bernd Blos at Shavemac, the owners could help with that.
As to what to do with your Duke 3. I would advise using it some more. To aid the softening of the tips, after use and washing out thoroughly, make sure to brush it vigorously each time on a dry towel with circular and paint brush motions. Some have even reported success with rougher tipped brushes with using it lightly a few times on sandpaper...not sure if I would go down that route unless you are really desperate. I have never tried it. Though I have brushed some of my "rougher" brushes when new on the fabric component of my razor strops, one a linen and the other the Kanayama Canvas which is quite rough. :) That also seemed to help.
I still own and have used some of the best boar brushes out there. But nothing, and I do mean nothing compares to a truly high end soft tipped badger with plenty of backbone. That is just my own 2c worth. Perhaps since it would be a Canadian 2c you could argue it is even much less... :gl:
