100% reliable? There is none. The limiting factor is Smeargle that can viably run any move and get any Moody boost that it may need. You can run dumb stuff, like Safety Goggles Darkest Lariat Incineroar, Clear Smog Infiltrator Chandelure, Haze/Perish Song Murkrow, or Safety Goggles Hyperspace...
Won in 3. gg's friend
Sableye-Mega @ Sablenite
EVs: 252 HP / 252 Def / 4 SpD
- Fake Out
- Foul Play
Mega-Sableye lures in Arc-Fairy, Xern, and Yvel, which can be Toxic'ed on the switch and Arc-Poison stalls them out when statused. Sableye additionally WALLS Pokémon...
Yes! Stall is a certainly a present play-style in AG (the viability of which can is disputable). You are right in that "walling" Mega-Ray is near-impossible, which is why AG stall focuses so heavily on hazard control. Pokémon like defensive Arc, Luna, and Lugia are able to check most Mega-Ray...