1. Make item 5 (D326) read 10 24 (Full Restore x36)
2. Make item 6 read 00 18 (j. x24)
3. Set item 30 quantity to anything you want (you can change it to control one of the encounter slots later)
4. Have cursor on Pokémon menu, then talk to Pewter Museum guy from right hand side using Rival's effect item (e.g. hex:94).
5. With the partially locked controls, use Fly (Pokémon 1 needs it beforehand) to go to Pallet Town
6. In Pallet Town, you should be able to open the items menu and use 8 8.
7. Use it, then Fly away again to Fuchsia City, change boxes at a PC and reset the game.
8. The automatic Start menu should be gone. Push the Strength boulder in the warden's house (requires Strength)
9. Locate quantity item D600 in the expanded PC (may be four below a Poké Ball x0 above the Master Ball x0) and change to x1 (enables Trainer-escape glitch)
10. Flash the Start menu and close it. Then, return to Route 6 and you should the menu open.
11. Use 8 8 and you should get a Trainer battle (no Special stats needed)
12. Use 9F to open the menu, and then save the game
13. Use Rival's effect item to walk on the water. (May be best not to save as unsure if saving again breaks the glitch)
14. Now, you will start fighting Pokémon you aren't supposed to in the water. It may often be MissingNo. and 'M. However, you can also fight the Pokémon you specified item 30's quantity to. Using this exact method, I was also able to get Mew. Hence, if item 30's quantity was x21, you may get double the chance of being able to grab a Mew. You can use another item 30 quantity like x195 to grab h Poké (hex:C3), etc.