I decided to ditch the BWOF men's shirt pattern. True, fitting the muslin on Tim would have been a valuable learning experience, but I figured - why reinvent the wheel when there are already several nice-fitting shirts hanging in the closet? So instead of learning to fit, I learned to trace a RTW garment.
First I pulled out several of Tim's G-Star button up shirts. I wanted a basic shirt to copy with a simple front, back, yoke, and sleeve. To my surprise many of them did not fit the bill - some have those pointy Western-style yokes, one has a dart or some kind of seam in the front chest area, a couple have princess seams in the back... these details are worthy of their own post in the future. Anyway, there was one no-frills garment among the bunch so I started with that.
I used two methods for tracing. First I tried Adriana's method of using Glad Press n Seal to trace the stitching lines of the front. I could only do this for one pattern piece because I was using a roll of Press n Seal that I already had in the house and it was nearly used up. Then I traced the shape onto tracing paper. I suppose you could use the Press n Seal as your pattern piece too. This method was very easy and I'm going to stock up the next time I find Press N Seal on sale.
Next I switched to David Coffin's method (as described in Shirtmaking) of sandwiching tracing paper between a shirt and a towel and using a pin to prick through the seamlines to mark the tracing paper. This worked nicely too. The only issue was that the fabric is kind of a loose weave, so I had to be careful not to stretch out the part of the shirt I was tracing.
Tracing a RTW garment was not nearly as scary or time consuming as I'd imagined. As long as the shirt muslin turns out decent, I can see myself doing a lot more RTW tracing in the future.