I have been submitting to IMDS since it's inception over here in the US. Back then, I found the training unhelpful to say the least and very few were using it so I had no other resources that I could use. I learned the system the hard way - I just jumped in and started using it but there were mistakes along the way. The most difficult part of it for me was that you can't use SDS's for your information. In most cases I found they were useless for IMDS. Especially when it comes to paints or anything that contains a solvent that will evaporate off after curing. I have become quite the chemist over the years.
It certainly isn't any easier but there are now many companies who can both train you and even perform the submissions for you. Google IMDS and you will find many willing to help.
Not sure how you have gotten this far without using IMDS? Every automotive customer we have, and some non-automotive, require IMDS. We wouldn't be in business without it.