Clarify feature flag dev workflow

Describe how to use feature flags when developing
a feature across multiple MRs

doc/development/feature_flags/development.md

@@ -32,8 +32,8 @@ request removing the feature flag or the merge request where the default value o
 the feature flag is set to true. If the feature contains any DB migration it
 should include a changelog entry for DB changes.
 
-In the rare case that you need the feature flag to be on automatically, use
-`default_enabled: true` when checking:
+If you need the feature flag to be on automatically, use `default_enabled: true`
+when checking:
 
 ```ruby
 Feature.enabled?(:feature_flag, project, default_enabled: true)

doc/development/feature_flags/process.md

@@ -21,6 +21,19 @@ should be leveraged:
 - Merge requests that make changes hidden behind a feature flag, or remove an
   existing feature flag because a feature is deemed stable must have the
   ~"feature flag" label assigned.
+- When development of a feature will be spread across multiple merge
+  requests, you can use the following workflow:
+
+  1. Introduce a feature flag which is **off** by default, in the first merge request.
+  1. Submit incremental changes via one or more merge requests, ensuring that any
+     new code added can only be reached if the feature flag is **on**.
+     You can keep the feature flag enabled on your local GDK during development.
+  1. When the feature is ready to be tested, enable the feature flag for
+     a specific project and ensure that there are no issues with the implementation.
+  1. When the feature is ready to be announced, create a merge request that adds
+     documentation about the feature, including [documentation for the feature flag itself](../documentation/feature_flags.md),
+     and a changelog entry. In the same merge request either flip the feature flag to
+     be **on by default** or remove it entirely in order to enable the new behavior.
 
 One might be tempted to think that feature flags will delay the release of a
 feature by at least one month (= one release). This is not the case. A feature
@@ -29,6 +42,8 @@ flag does not have to stick around for a specific amount of time
 is deemed stable. Stable means it works on GitLab.com without causing any
 problems, such as outages.
 
+Please also read the [development guide for feature flags](development.md).
+
 ### When to use feature flags
 
 Starting with GitLab 11.4, developers are required to use feature flags for