db_query() not compatible with IN operator?
You can use placeholders in IN conditions, but you need to set them up correctly first.  Using the example in your first link, this should work:

$replacement_values = array();
foreach(array_values($your_values) as $i =&gt; $val) {
  $replacement_values['@val' . $i] = $val;
}
// Should look something like:
// $replacement_values = array(
//   '@val1' =&gt; 'your first value',
//   '@val2' =&gt; 'your second value',
// );

$placeholders = array_keys($replacement_values);
$placeholders = implode(', ', $placeholders);
// Should look something like:
// $placeholders = '@val1, @val2';

$res = db_query('SELECT field FROM {table} WHERE cond_field in(' . $placeholders . ')', $replacement_values);


n.b. I haven't tested this so it might need some tweaking.

That said, I'd urge you to look into dynamic queries.  They're not that hard to get your head around and if you wan't to right modules that might ever be used on another Drupal site that uses an alternative database to MySQL then they are a must.