Reverse proxy separate Wordpress instance

apache.conf

<VirtualHost>
...
### START - Blog redirection
RewriteRule ^/blog$ /blog/ [R=301]
<Proxy *>
  Order deny,allow
  Allow from all
</Proxy>
ProxyRequests off
ProxyPass /blog/ http://url.of.separate.blog/
ProxyPassReverse /blog/ http://url.of.separate.blog/
### END - Blog redirection
...
</VirtualHost

nginx.conf

server {
...
  location ^~ /blog {
    proxy_set_header X-Real-IP  $remote_addr;
    proxy_set_header X-Forwarded-For $remote_addr;
    proxy_set_header Host url.of.separate.blog;

    client_max_body_size 10m;
    client_body_buffer_size 128k;

    proxy_max_temp_file_size 0;
    proxy_connect_timeout 90;
    proxy_send_timeout 90;
    proxy_read_timeout 90;
    proxy_buffers 32 4k;

    proxy_redirect http://url.of.main.site/ /;
    proxy_redirect http://$host/ /;

    proxy_pass http://url.of.separate.blog;
  }
...
}