Break it up into segments. Grab -> Release -> Jump, Grab -> Release -> Jump, repeat. Get that timing, then put in the airdash once you are releasing and jumping as quickly as you can. If you are suiciding, learn how you can compromise a couple frames of invincibility for a bit more consistency, and then tighten it up from there. Higher is safer, but less invincibility. Remember that.
Also find out what is more consistent for you, pressing down or pressing away to release. I personally use Down because it is the same regardless of side and I don't have to rotate the control stick as far.
If you are doing ledgejumps (tournament winner) you are pressing jump before you've released the ledge or pressing to release the ledge before you are able to. Take notice of your timing and make an alteration.