Call me picky but I consider several of the suggestions made in the NSSA link to be bordering on extremely dangerous.
While reducing the amount of engagement the nose of the sear has with the full cock notch of the tumbler will reduce "creep" it will not lighten the trigger pull. On the other hand, it can easily make the gun totally unsafe to shoot.
Carried a bit too far, the gun will be prone to shooting itself with the slightest bump.
IMO, the usual cause of a heavy trigger on a replica Civil war gun boils down to several things.
First of all, these were guns intended for field use and a heavy trigger was seen as a asset for poorly trained solders. They were less apt to accidentally fire their weapon.
Next, there is no doubt that the surface roughness of the tumbler notches is rough. Lightly polishing them (without changing their angles or rounding off their sharp edges) can help quit a bit.
I did agree with the links comments about modifying the sear spring. These are typically about twice as strong as they need to be and reducing their width can improve things greatly.
Do not shorten them though. Although some may think that would help, exactly the opposite will happen if the leg of the spring is shortened.
Another common problem can be as simple as the tightness of the sear pivot screw.
This screw is often tightened. If this is done the sear will be pinched between the lockplate and the bridle making it almost impossible to move.
This screw should be run down until it is snug. Then back it off about 1/2 turn.
In this condition the sear will be free to move without undue slop. If your concerned about the screw changing its setting, a drop of LocTite on the threads will keep it in place.
