the blogengine slug removal does not work because the other slug rule is first

[jphellemons]

so you have to swap the order of the slug url rewrite rules in the web.config:

<rule name="BlogEngine slug" stopProcessing="true">
          <match url="^post/(.*)\.aspx" ignoreCase="true"/>
          <action type="Redirect" redirectType="Permanent" url="/post/{R:1}"/>
        </rule>
        <rule name="slug" stopProcessing="true">
          <match url="^post/(.*)" ignoreCase="true"/>
          <action type="Rewrite" url="/?slug={R:1}"/>
        </rule>