Dont masturbate.
Masturbation will give you something called sexual exhaustation. Your erections wont be as strong and there fore you will leak and come quick.

Workout to hold ejaculation
you know that musscle you tense when you hold your pee? Well you need to exercise that muscle.
Do it anywere cuz nobody will notice you are doing it.
Basicly in ten seconds hold and let go as if you where holding your pee. It should feel like sqeezing your buttcheeks. Do 10 in 10 seconds, rest for ten seconds. Do this for at least 5 minutes daily so it will be 5 sections of one minute. It looks like a lot but trust me its worth it and you can do it while having lucnc. Start with this for 1 week. After that you can do it as much as you want to keep building that muscle but remember like any other mussle it will get soar so start slow and then increase.

Also look at the other tips I gave you in other posts