Most large companies (should) have had their programmes around GDPR in progress for at least a year now. Are you a small/medium size org?
Regarding training - well it depends on what your role is. Specific training on how to respond to a SAR or RTBF (which doesn't have to be justified) or in Data Privacy or Security or an industry sector specialisation? There is training available in all these areas. Some of it is actually useful.
Certifications may not help you do your job. Even the BCS is not cheap or widely recognised although a useful basic framework.
I'm dealing with databases that are not user friendly and I'm going to have to do all the data capture manually.
What do you call large or unfriendly? If all the data capture is manual I'm guessing you are a small org with little technical help available?
The rules don't only apply to structured (database) stores. Data held in emails, random files, backups, recordings of phone conversations, video recordings (eg cctv) is all in scope. It also includes test data iwhich may need anonymising or pseudonymising (HMRC have indicated the latter for financial records)
Sending out a mailer to ask for opt ins is likely to get a 30% open rate if we are lucky. How can we get around this?
That isn't really the point - you should be aiming for compliance. Your approach of "opt in or you will miss out" is the right mindset, "fail to check box 194 iin invisible ink and we keep your data" is the wrong mind set.
As well as the ICO you will find useful free information and guidelines at:
gdpr-info.eu
Some organisations are opening up their process and frameworks for free reference eg:
www.nymity.com/gdpr-toolkit.aspx
Most big consultancies have a large amount of info including toolkits and guidelines for free as do vendors. Big 6 will be vendor agnostic typically, vendors obviously have a bias to their own products.
@amaliaa metioned charities and very small orgs.
Most big consulting firms have sizeable pro bono groups who will offer ad hoc advice/support to registered charities or small NFPs. Its worth asking.
If you have a volunteer who works in 'Big' consulting, or has a family member so doing, then ask them to find out. If not look for charities pages on Big4/6 websites - they don't only help large charities. As well as advisory help they will often share additional content on a no-liability basis which could be useful to get started.