I also found this issue a problem while making the pin board. I also found out, that nobody every mentions this problem in videos or write-ups on dovetailing…I wonder why, because I find this part of making the pin board quite challenging to make it neat and clean. The method I tried using recently is to chop in from the narrower side of the tails (wider of the pins) which leaves a little triangle of wood (widening towards the wider side of the tails), which I then pare down with the chisel. I find this more accurate and cleaner than chopping with the chisel at an angle.
I hope this might help…and that someone finally pays some detailed attention to this matter in a video tutorial 🙂