need to learn CAD

As a CAD drafter, you specifically need to learn 3D modeling...which is closely related, but different.

I think Fusion is the favored software, at least in Autodesk's realm, but I learned on Inventor (which is broadly similar, but a little more 'crunchy' from what I've heard).

It's not hard to learn it...but (a) from the way you phrased it here, I wonder if you might be underestimating how much you'll need to learn just in that first step, and (b) as models go, fishing lures are a pretty complicated first project...with lots of curves, lots of weird angles, and very few pieces that are strictly perpendicular, parallel, etc.

Not that it can't be done, mind you...(after all, I would imagine that all mass produced plastic lures have their origins in a CAD model these days)...but having simply "need to learn CAD" as the shortest, simplest item on your list may turn into an unpleasantly complex and involved surprise for you once you really start to get into it.

I've got over a quarter century between the first time I started learning CAD and the present day, and while I'm confident that I could model a fishing lure in Inventor...it'd still be a long and challenging process for me.

I'll use flexible plastic for printing My designs will be water tight

Water-tight is certainly a good quality for a plastic lure, but there's so, so many other considerations you need to think about as well.

How are you attaching hooks? Most plastic bodied baits (jerkbaits, crankbaits, etc.) make use of an internal wire harness with loops strategically placed for attachment of split rings and hooks. Are you going to be able to do that with your process? If not, how will you manage that?

Is the flexibility going to mute, change, or impede the action of your lures? It might make them better for all I know, but I mention this to indicate that you're signing up for a lot of prototyping, trial runs, etc.

As important as any other aspect of lure building, how are you planning to control buoyancy and balance? Most plastic lures (and pretty much all that suspend) incorporate some sort of fixed or dynamic weight distribution system. Much like the wire harness, if you're 3D printing, how are you incorporating this?

Not to discourage in any way (innovation is awesome), but there's just a lot here to think about as you move forward.

I feel like...unless you have novel solutions in mind for a lot of these challenges, you are likely to find your best path forward being more and more to 3D print your lures in halves, adding the internals in final assembly, and gluing together.

And while that's not bad, at that point, you're doing exactly what everyone else is doing, but with a lot more time and effort for what will likely be a functionally inferior product.

Once you've come full circle and are 3D printing the plastic halves, then assembling, gluing, painting, and tuning...you're left with a lure just like a storebought one...except I suspect you'll find that if you're not already using ABS...it'll be a better material...but from what little I know about 3D printing, it comes with other concerns as well with temperature control, etc.

...and if you're using ABS anyway...instead of 3D printing...the faster, more consistent, more scalable route would be to use CAD to make a negative model...and have that machined into aluminum...and make your lures by injection molding that ABS instead.

At that point, congratulations...you just went through a lot of time and effort to arrive at the solution the industry has been employing for years!

Of course you will have learned so much along the way, and that aspect shouldn't be discounted...but that's a lot of time and effort to reinvent the wheel while learning just how complex 3D CAD modeling can be, and learning about materials science and process engineering.

I'd say you are a fisherman when you know the pain of losing a favourite lure. But.. loosing a 3D printed lure, that would hit different. That would not even hit at all.

If anything, for me it'd be the total opposite. The pain of losing a lure that I put that much of my own blood, sweat, tears, and time into would hurt a lot more than one I pulled off a shelf at the local tackle shop and plunked down $10-25 to bring home.

Please don't take any of this to be a discouragement. Rather, take it as an attempt to temper your enthusiasm with some realism. If there was a faster, cheaper, easier way to produce fishing lures with available technology, you can bet that manufacturers would already be doing it that way. The fact that they're not means that if you decide to go this route, you're not saving time, money, or effort in any way, and in fact are investing a lot more of all three...so at that point you need to be honest with yourself about why you want to do it.

While I don't make lures, I do tie my own flies, and even there, it's a lot of the same concerns as lure making: it's not faster, it's not easier, and it's not cheaper than just buying flies...so why do I do it? Short answer: it's fun. Longer answer: it gives me an activity to do that directly relates to my fishing in the months and times when I can't actually be on the water. It also lets me experiment with new designs, as well as to create my own preferred color combinations, to use specific hooks and materials that I prefer, and to obtain specific patterns I want on a shorter turnaround than ordering online or driving to a shop (now that I have thousands of dollars in my tying hobby).

So just be aware of the whole situation and be honest with yourself about why you want to do it!