Why not use Custap? Subbing down to Custap range is all kinds of threatening to your opponent, if you can force something out and make them switch something in that's faster.
Exeggutor @ Custap Berry
252 HP/252 SpAtk/4 Def
Quiet (0 Spe) / Harvest
Substitute
Psychic/Psyshock
Grass Knot
Hidden Power Fire/Hypnosis
He gets great 3-move coverage if you use this with Sun (only reason to use a set like this, a mere chance of getting your custap berry back makes it worthless). If you get your ideal setup, 2 chances to put a fast opponent to sleep is pretty worthwhile too though. Psyshock should go with Hypnosis, since it gives you a legitimate shot to get past Chansey without bringing in Victini, since it does 186 - 219 (26.42% - 31.11%) vs. 252/252 bold eviolite chansey, the most defensive version possible. Minimum speed means your sub will be broken first by basically everything, which will let you get into Custap range while keeping your substitute.
Exeggutor @ Custap Berry
252 HP/252 SpAtk/4 Def
Quiet (0 Spe) / Harvest
Substitute
Psychic/Psyshock
Grass Knot
Hidden Power Fire/Hypnosis
He gets great 3-move coverage if you use this with Sun (only reason to use a set like this, a mere chance of getting your custap berry back makes it worthless). If you get your ideal setup, 2 chances to put a fast opponent to sleep is pretty worthwhile too though. Psyshock should go with Hypnosis, since it gives you a legitimate shot to get past Chansey without bringing in Victini, since it does 186 - 219 (26.42% - 31.11%) vs. 252/252 bold eviolite chansey, the most defensive version possible. Minimum speed means your sub will be broken first by basically everything, which will let you get into Custap range while keeping your substitute.