Most of the clothing I make for myself is from BWOF or Burda Plus and I'm always looking for ways to make the process easier. I used to trace off the pattern pieces, pin them to the fabric and add the seam allowance while cutting using a rotary cutter with adjustable arm. A few months ago, I didn't have enough fabric for a project and I had to cut and squeeze and eliminate hems and pray that the pieces fit on the fabric; remembering to leave enough room to add the seam allowances. It would have been simpler if the seam allowances were already included on the pattern pieces. So, my newest favorite notion for adding seam allowances to patterns is an ordinary compass.
I read this tip on Pattern Review, but until recently, I rarely used it. I adjust the compass to the desired width and add the seam allowances. I run the point of the compass along the seam line and the cutting line is added! It took some experimentation to find a way to hold the compass and apply the pressure needed to make a mark. The compass doesn't have to be anything fancy. One thing to keep in mind is the point of the compass – a plastic point that won't tear the paper is better than a sharp metal point. (A lesson I learned the hard way.) I also occasionally check the compass against a measuring gauge or ruler to make sure the distance between points remains constant.
Using a BWOF pattern is more labor intensive than using most other patterns. I have to read the directions very carefully. Sometimes, I have to consult outside sources. But I'm usually pleased with the results. The more I use them, the easier it gets.