A release can be perform as simply as;
$ ./mvnw -PreleaseSonatype checks that a release is signed. Using settings.xml define which key to use and it's password;
<properties>
<gpg.keyname>0xMY_KEYID</gpg.keyname>
</properties>
<servers>
<server>
<id>0xMY_KEYID</id>
<passphrase>PASSWORD_AS_PLAIN_TEST_OR_ENCRYPTED</passphrase>
</server>
</servers>