To use track pins or not to use track pins?
I personally dont like track pins. What I will be doing when my baseboards have been built is using the method our club layout uses. The track is pinned in place with dress makers pins (those that have the nice big plastic balls on the end) then ballasted. Once the ballast is dry the dressmakers pins are removed. A prototypical approach as real track is held in place by its ballast, and in areas where the track has been prone to slippage, they "glue" the ballast to hold the track, a bit like fact following fiction!
Steve