"Custom Training" really means Custom Documentation
Live training is just one, occasional way to consume the content.
I develop training; it's one of my favorite things to do. It's a Maximum Resource Multiplier.
If you're considering developing custom "training", whether you do it yourself or contract it out, think beyond the old paradigm of expecting a big static PDF. Think beyond that one-off of an instructor monologuing to an audience (or two or twelve).
Maximize your development value.
Consider how your staff would best consume "training"
I have written many 200-page training manuals. That's old school. Learners don't learn that way any more, unless they're full time students. Full time designers need easier-to-consume training, as in short well-scoped modules. They just want to get unstuck and get back to progress as fast as possible.
You do not need a comprehensive omnibus 900-page custom training start-to-finish step-by-step monument that requires an ultra-guru to teach in person. Unless you're a government agency, and then you might have to (process-priority vs. outcome/value-priority).
Your staff needs documents where they know what to do, whether it's a project roadmap or a workflow cheatsheet or an explanation of how their required process deviates from the general training that is freely available.
Multiple 10-page documents they can find easily is how they will move their projects forward without having to take time off from production (billing!)
Training - instructor-led training - is a periodic, often rare event. Success is continuous. Design your custom "training" to be easily, continuously useable. Without an instructor.
How will you Serve your Custom Content?
After you realize that most learning, most value, is asynchronous - NOT live - you are freed from a lot of outdated obsolete assumptions.
The first decision to make when you realize tht custom "training" is simply process documentation is "how do we store and serve this information?"
The number 1 rule is: it has to be FINDABLE.
It can be as simple as a file folder location and good file names. This is the most common (but least extensible) system. After working within Microsoft Teams extensively I have reluctantly conceded that, due to its poor navigation interface, that I have to backstop all the important information in a single folder tree with explict folder and file names. If the "Navigation" and other curating capabilities fail, the good ole'fashioned Browsing Through Folders and Files provides a brute force "findability".
Teams is messy, but interactive and collaborative, Sharepoint is cleaner but hard to get much collaboration on.
I prefer websites like this. They're ultra powerful, Search works great, but it takes a couple of weeks to get an administrator up to speed.
There are ways to deliver a richly hyperlinked (hyperlinks MAKE the web) documents with inexpensive and simple to use HTML editors (like $29 CoffeeCup). They provide a rich web-like experience that is completely file-based. They are a nice balance between simplicity (in authorship and use) and power.
Do you need to Re-create the Wheel?
Foundational training by definition needs to be broad-based and very protective/nurturing of new users. Hint: foundational training is pretty well covered by the Software Vendors, and it tends to be freely available with the software licenses. Do you want to pay a lot to re-create that wheel? Or do you want to pay much less to leverage that wheel? The software vendor libraries are large, continuously updated, and "streamable".
There is plenty of opportunity to accelerate (xlr8!) your productivity by filling the gaps in what the vendor publishes.
Prioritize!
Like any complex process, prioritize the big opportunities. Fix the big problems first and fast.
You do not drink a week's worth of coffee in one sitting. You don't learn that way either. Consecutive-day training is done for optimizing logistics, not optimizing learning. Get a good-sized cup early. Get more later. That's Agile.
Do NOT contract a training develop to deliver a static, uneditable document, like a hardcopy or a PDF. Demand an editable source document as a deliverable. Your in-process support documents need to be easliy updatable so that they're live not an increasingly incorrect snapshot.