I have a simple website developed with the Grav CMS. Now, it has many pages and I really want to migrate it to the WordPress CMS.
Is there anything to do in order to make the migration process smoother and pain free?
Short answer: not really, not currently.
Apparently there were some plugins that tried to generate Grav pages (Wordpress plugin) and for importing from export.xml (Grav plugin) but both do not currently work (they have aged a bit).
As far as plugins go, it is pretty much a need to find equivalent plugins and manually install/configure.
As far as themes go, there are some themes that work on wordpress and grav (though I believe they are different actual themes, they have versions for grav and for wordpress. For example, see rockettheme.com
Note that for things like installing/updating themes and plugins, the CLI (command line interface) is fast and effective.