Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison
With experience, you will get faster and straighter (that said, 20+ years, and I still make some crooked prints.A good way is to pull the shirt fully on until the shoulders snug against the top of the board, then back it evenly towards you until in the correct position.You will also start seeing the knit for straightness as well.
That guy lost a little credibility (with me) when he pulled out the spray tack.