This is an example of two ways to query the same posts.

WP_Query() meta_query vs post__in

<?php

$array_of_data = array('Array','Of','Data');

/**
 * meta_query WP_Query
 **/

$query = array(
	'post_type'		=> 'custom_post_type',
	'post_status'		=> 'publish',
	'posts_per_page'	=> -1,
	'orderby'		=> 'menu_order',
	'order'			=> 'ASC'
	);

if ( is_array( $array_of_data ) ) {
	$query['meta_query']['relation'] = 'OR';

	foreach ( $array_of_data as $meta_value ) {

		$query['meta_query'][] = array(
			'key'		=> 'meta_key',
			'value'		=> $meta_value,
			);
	}
}

$wp_query = new WP_Query();
$wp_query->query( $query );


/**
 * post__in  WP_Query
 **/

global $wpdb;
$meta_value__in = "'" . implode( "', '", $array_of_data ) . "'";

$querystr = "	SELECT $wpdb->postmeta.post_id 
		FROM $wpdb->postmeta 
		WHERE 
			$wpdb->postmeta.meta_key = 'meta_key' AND 
			$wpdb->postmeta.meta_value IN ( $meta_value__in )
			";

$results = $wpdb->get_results( $querystr );

$post_in = false;
foreach ( $results as $result )
	$post_in[] = $result->post_id;

$query = array(
	'post_type'		=> 'post_type',
	'post_status'		=> 'publish',
	'posts_per_page'	=> -1,
	'orderby'		=> 'menu_order',
	'order'			=> 'ASC',
	'post__in'		=> $post_in,
	);

WP_Query() :: meta_query vs post__in

<?php

$array_of_data = array('Array','Of','Data');

/**
 * meta_query WP_Query
 **/

$query = array(
	'post_type'		=> 'custom_post_type',
	'post_status'		=> 'publish',
	'posts_per_page'	=> -1,
	'orderby'		=> 'menu_order',
	'order'			=> 'ASC'
	);

if ( is_array( $array_of_data ) ) {
	$query['meta_query']['relation'] = 'OR';

	foreach ( $array_of_data as $meta_value ) {

		$query['meta_query'][] = array(
			'key'		=> 'meta_key',
			'value'		=> $meta_value,
			);
	}
}

$wp_query = new WP_Query();
$wp_query->query( $query );


/**
 * post__in  WP_Query
 **/

global $wpdb;
$meta_value__in = false;
$meta_value__in = "'" . implode( "', '", $array_of_data ) . "'";

$querystr = "	SELECT $wpdb->postmeta.post_id 
		FROM $wpdb->postmeta 
		WHERE 
			$wpdb->postmeta.meta_key = 'meta_key' AND 
			$wpdb->postmeta.meta_value IN ( $meta_value__in )
			";

$results = $wpdb->get_results( $querystr );

$post_in = false;
foreach ( $results as $result )
	$post_in[] = $result->post_id;

$query = array(
	'post_type'		=> 'post_type',
	'post_status'		=> 'publish',
	'posts_per_page'	=> -1,
	'orderby'		=> 'menu_order',
	'order'			=> 'ASC',
	'post__in'		=> $post_in,
	);