I have been away from the game for months, but I have come back in this event with my signature SOLO Smeargle. These builds are difficult to make and require a lot of luck and patience BUT is oh so possible! Blissey has more base stat in her HP than Smeargle has in ALL of its base stats combined, but NEVER underestimate an unlimited movepool :)
Sceptile clears buffs close to the very beginning of the raid, so actually its ideal that you get taken out with a "leaf storm" t0, so you can return and never have buffs removed again. You have to play this raid by ear, so this is NOT for a beginner at all. I decided to go aggressive and went for the belly drum and from there, RNG and some solid execution on my end led to the dub!
NPCs recommendation: two intimidators. Arcanine is the best NPC with intimidate AND leer as support moves. After you get the two intimidators; Drifblim (will-o-wisp to burn sceptile) is the best third option, followed by Sylveon (charm, to reduce sceptiles atk -2), Weavile (leer, to reduce sceptile def -1). You can have PERMANENT NPCs for each raid.
Smeargle @Shell Bell Lvl 100
Nature: Adamant l All hypertrained
EVs: 252 ATK l 252 DEF
-Belly Drum
-Glacial Lance
-Thunderous Kick
-Burning Bulwark