I’ve levelled entrapment on a few characters over the years and always use the same method.
Go to the trainer in bichon wall, spawn an arcaman and go and stand in the corner in a straight line to the trainer, your arcaman will instinctively go and attack the trainer, assign entrapment to F1, change attack mode to attack all, highlight your arcaman and the put your bag over it, and move the cursor into your bag with arcaman still highlighted, force F1 down on the keyboard using a bit of paper, and leave overnight.
Your pet will perpetually be pulled back to you then walk back to the trainer all night long