Here are some cards you will need to add to make this farm deck work against certain duelists.
Yugi Muto: Abyssal Designator - Use this to get rid of Sphere Kuriboh. Sphere Kuriboh can stop your Winged Dragon of Ra's final attack leading to a deck out loss.
The higher leveled Sylvan monsters all have effects to excavate cards from the top of your deck and this can be done once per turn, use these effects as often as possible to quickly thin your deck. Aside from that they also have effects when they are excavated from your deck.
Sylvan Komushroom is your way of destroying troublesome spell/trap cards on the field. His destruction effect activate when he is excavated, but aside from that you can also use him to excavate cards from your deck by placing him face-down and having him flipped face-up.
To help you Winged Dragon of Ra reach 10,000+ attack, activate Solemn Wishes as early as possible in the duel. You can activate 2 of them for faster results. By the final turn of the duel when you summon Ra you should be able to easily get him above 10,000 attack.
On your final turn you must have 3 monsters on your field, preferably the strongest monsters possible. Activate Hey, Trunade to return all set spell/trap cards on the field to the hand. Enter the battle phase with your 3 monsters and destroy all monsters your opponent controls, do not finish the duel yet. After you have cleared the board activate Arrivalrivals to summon The Winged Dragon of Ra from your hand. Activate The Winged Dragon of Ra's effect and attack for game.
You may sometimes fail to finish the duel with The Winged Dragon of Ra due to your opponent setting some form of monster removal during your final turn, like Seto Kaiba with D.D. Warrior or Yami Bakura with Man-Eater Bug. For these Duelists you have to add piercing damage (i.e. H - Heated Heart, Fairy Meteor Crush, Big Bang Shot) to your deck. summon The Winged Dragon of Ra during the main phase of your final turn and then use the piercing damage on him. This strategy can be used on any Duelist but it is best to only use when necessary as it lessens the consistency of your excavations and increases the number of turns to end the duel.