Frank, ref your question on how Tin Star meters, according to the Handloader article, Vandenberg advised the powder was small 'kernels' compared to TrailBoss being flakes. Should meter better. I don't use a progressive reloader, but from experience and from what has always been written about powder metering, the small kernel and ball powders seem to always meter better. I've had the occasion of some of the larger flake powders being 'not as smooth', but never a big enough problem to cause any or significant difference in load accuracy. TrailBoss meters fine in my RCBS powder measure.
Ref your question about how TrailBoss and Tin Star compare in 'the clean burning area', he states that Tin Star is a little cleaner burning and is also a slower burning powder than TrailBoss, sort of in the area of Win 231.
To answer the third part of your question "or what" is the best powder for 45 Colt, I'd say whatever powder of the many that work best for your handgun and IS readily available. PJ in his post wrote of the use of "shotgun powders, Unique, Red Dot, Green Dot, and 700X. All would work, I've never used Green Dot and have found 700X to be a dirty burner(in my exp). Have reloaded many 45 Colt using Red Dot (a favorite and one of the powders I load a majority of 45 Colt with) and a lot using Unique, both excellent. As PJ, Don, and Gus stated, Unique is a great powder for the 45 Colt. Unique is properly named as it is "Unique" in that it works well for most calibers, including some rifle. I've loaded a lot of reduced cast bullet loads for my military bolt action rifles using Unique and Red Dot. I've never have used Unique for shotgun, but a lot of 12 gu trap loads with Red Dot. If I were to limit myself to just a handful of powders or even 2-3, Unique would be one of them. I've loaded revolver loads from 38 Spec, 357 Mag, 44 Spec, 44 Mag and 45 Colt with it. As stated, its cleaner burning now than it used to be back when Hercules owned the company. I've never used it for 45 Colt, but have seen load charts for it, but Hodgen TiteGroup is an excellent powder. I've loaded it in 45 ACP with excellent results. Clean burning, accurate, and it is one of Hodgens line of powders that ISNOT position sensitive in the case. One of its advertising selling points. A good advantage for smaller powder charges in a large case such as the 45 Colt. Two other powders that I've used are Winchesters 231 and Hodgons HP38. Both are basicly the same powder in different containers. The only drawback with these two are the large airspace in the large 45 Colt case, but both good clean burners, accurate. Could always do as Cliff suggested, use blackpowder. I don't load to many 45 Colt with it(a lot of 44 Colt rounds though for my Colt Richards II and Open Top), but black is a good shooter and a lot of fun.
I mentioned about having a good powder 'readily available'. Whatever sparked your interest in Tin Star and if you can get it and develop some loads, make sure you can get when needed and don't have to search 'the highways and byways' to replenish your needs. According to Vandenberg, he waited some time to get some and that was through a Hodgon Powder rep at 'the 2013 Shot Show (a year ago-I don't know when he wrote the article, but it just was published with the newest Handloader issue). VanDenburg states in his article that Hodgon is now the US distributor for Vihtavuori Powders (from Finland). I checked both Hodgons and Vihtavuori websites, neither made mention of any connection. Guess I said all this to say this-develop your loads from what you can buy and get again, locally if possible. Where I live in the North Iowa/Southern Minnesota area, the Vihtavuori powder isn't seen that much, at least in the places I go, so I wouldn't bet my loading projects on it. Not to say Tin Star and all the Vihtavuori powders are not good products. I doubt if I will use Tin Star, I have to many powders now, keep tryin' to cut back, but its hard to get rid of 'old friends'! Good luck in your loading, I enjoy reloading as much as shooting, never seeing it as a dreaded chore-except case trimming, hate that part with a passion. Yours, Crow Choker