Of note is the fact that neither method constitutes a proper Fusion Summon.
If using "Miracle Synchro Fusion", "Gale Dogra" can send both of the "Naturia" Synchros to the Graveyard from the Extra Deck, albeit at the high cost of 6000 Life Points. This is the fastest way to Fusion Summon, but is expensive. One can try summoning one of the "Naturia" Synchros and then using Gale Dogra's effect once, requiring more cards but costing 3000 Life Points less.
An alternative, less costly way of using "Miracle Synchro Fusion" is to use "Zaborg, the Mega Monarch" to send multiple copies of "Naturia Beast" and Naturia Barkion. With this method, you can use "Miracle Synchro Fusion" to summon up to three copies of "Naturia Exterio" if your opponent happens to be able to destroy it and send vital cards from your opponent's extra deck to the graveyard.
With "Naturia Barkion" and "Naturia Beast" on the field and "Super Polymerization" in hand, it is possible to deal a total 7500 damage. While the point of these monsters is to prevent the opponent from activating certain cards, the sheer damage output is helpful as well (as well as providing at least one card in the Graveyard that can be removed without worry).
If using "Naturia Cherries", have it destroyed in order to Summon two more. Play "Instant Fusion" to bring out "Karbonala Warrior", then tune it and a "Naturia Cherries" to bring out "Naturia Beast". Then, tune the other "Naturia Cherries" and "Naturia Beast" to bring out "Naturia Barkion". Finally, play "Miracle Synchro Fusion" and remove both "Naturia Beast" and "Naturia Barkion" to bring out this card.