Chansey Growl could work. Then again Reflect does the job better generally.
And standard Lapras is: Blizzard/TBolt/B-Slam/CRay, although I think Sing is at least as good as CRay.
I would love to face a resting one as it would give me a chance to CH it before it can even explode. Rest is overall a pretty poor move in RBY, I feel, and pretty much only belongs on the Amnesia pokémon.
Well there's plenty of pokemon with Reflect that can use it (Hypno and Snorlax are probably most popular). Rest Cloyster works reasonably well as long as you have something that can absorb the incoming Thunderbolts. It also makes the Explosion less predictable. Oh, and can still easily come in on Blizzards when asleep, which can come in handy too.