Make sure you are keeping pressure on the outside leg and outside rain making their head tilt slightly outward. Once you have continued giving your horse clues it should get a lot easier. When your horse does pick up the correct lead, make sure you reward them so they know they are doing the right thing. Also lots of practice helps and make it easier! Hope this helps!
-Support the outside shoulder of the horse with your rein and lighten the horse’s inside shoulder.
-Keep the contact with the inside rein, but stay neutral.
-Lean on your outside buttock by lightly putting your outside shoulder back.
-Ask for the canter depart by putting your outside leg back and touching lightly.
-Keep your inside leg at the girth.
To be on the right lead after a jump, always look where you want to go and most of the time it is enough for your horse to be on the right lead.