You can try doubling up the fly line to make a channel to feed the leader back through. It works every time and no need for tools.
1. Fold fly line over
2. Make wraps very tight around flyline
3. Slide leader back through the channel between the doubled up fly line
4. Slide doubled up part of fly line out
5. Knot should already be very tight but pull tight a little more
I struggled with nail knots forever until I discovered this method. Now I can do twelve wrap knots that are perfectly alligned on the first try every time.