I don't have an overview of all steps required but provided you do this then GA should still be allowed to be used without explicit user permission.
https://support.google.com/analytics/answer/2763052?hl=en
Of course, that doesn't stop that IP address becoming aware to the GA servers, but they should stop it being used further down the line.
I suspect it's similar to using a CDN where the IP address again is passed to a third party.
The original plan was for both the GDPR and the ePrivacy Regulation [1] (not to be confused with the ePrivacy Direcive) to come into effect on 25 May 2018. The ePrivacy Regulation would have had a special exemption for analytics cookies. If that would have been enough to not require consent for Google Analytics I do not know.
Now the ePrivacy Regulation is delayed but the GDPR is not. I didn't find a lot of information about what that means for the time after 25 May 2018. The following is from German sources (primarily e-recht24.de [2]) and is only from a German perspective.
Google's terms [3] in accordance with German law currently require consent in the case of AdSense but not for Google Analytics. According to [2] this is in obvious conflict with current EU law but the EU Commission denies that.
e-recht24.de [2] is careful to avoid a clear statement about the situation after 25 May but from my understanding they hint that the situation will not change. German law is already in conflict with EU law and this fact is ignored by all parties. The GDPR will not change that situation.
[1] https://en.wikipedia.org/wiki/EPrivacy_Regulation_(European_...
[2] https://www.e-recht24.de/artikel/datenschutz/8451-hinweispfl...
[3] https://www.google.com/about/company/user-consent-policy.htm...
One of the caveats though, is that you shouldn't be able to identify a specific user. So, you would need to anonymize the IP addresses you're tracking [1]. My understanding is that you should not be tracking or storing information that can be used to identify a single user. So cookies are ok, but you have to ask permission for any cookie that can be used to personally identify a user.
[1] https://developers.google.com/analytics/devguides/collection...