Is it just me, or her dash grab has really good range? It seems like she slides a bit as she does it.
I like to play her a bit like wario and airdodge all over the place. You can airdodge into grabs and with her aerial mobility you can weave in and out, and land in front or behind the opponent. Just pressure with wall of pain, mix in airdodge into grabs. You can condition your opponent into shielding your double aerials, then do only 1 and airdodge into grab, see? I say that because if you don't mix in grabs with her, you're nerfing her abilities a lot. Every grab hit does like 3%, plus the 10% throw.
Yeah I just went back to page 1, and g-reg pretty much said it all lol. I remember a convo we had from CoT4 about jiggs, he knows his stuff.
Also, dair is weird... you can like, sh or full jump dair and weave in and out while hitting someone's shield, and decide whether to land next to the opponent if it shield pokes or not. If it doesn't poke, then you're out of range and their shield is reduced, so they you can decide to keep pressuring or wait for their response passively. If you land it, you should be able to grab at least. Against snake though, don't short hop dair on his shield, that's a free ftilt. Of course, use common sense.
Yeah it's all I can think of at the moment. Of course, she's not one of the good chars in the game, she has glaring disadvantages like her weight and killing options, but she can be used well like most chars in the game. It's always an uphill battle, but as long as you concentrate on pushing your opponent off stage and getting the grabs, you should be on the right track. If you just rely on your aerial game to dish damage, you will get wrecked.
Brawl isn't really like fencing (melee), it's more like chess, so take it slow. It's like, if you get in the opponent's face too much, you're giving him that many more opportunities to punish you. This is especially the case with Jigglypuff. You don't have a big margin for errors.
For KOs, I find that rest is really really hard to connect with. It's so hard to punish a missed recovery or an airdodge with it, the hitbox is way too small. You also die at like 40% against a lot of characters after missing a rest, so you can only really use it at low percentages... very low >_>. Fair is really good, but you have to land it on the edge of the stage. Fsmash has a lot of start up frames, so you kinda have to Ike the forward smash, and bait airdodges. I have a lot of trouble landing utilt, but I think it's a killing move when fresh? If anyone has input on that, please share.
I'd also suggest getting used to pressuring opponents off stage, don't be afraid to jump off to get an airdodge from them and fair them for the KO. Also, when you jump off stage to edgeguard, make sure you don't let the opponent get past you, always pressure in the air, but retreat towards the edge so you can get him to go lower and edgehog.
That's all I have right now. Also brawl is getting very boring. Also G-reg is pretty much the most knowledgeable jiggs poster from what I've seen in this thread, he said most of what I was already thinking.
EDIT 2: About powershielding into rest, the mechanics of the game allows you to do so, but only when there's really really bad spacing, or if the opponent's move carries the opponents character over jigglypuff. I've powershielded a TL dash attack into rest a few times.
And about multi hit moves, just like edreese said, you can interrupt them with rest. If you get jab comboed, just mash down B. One example, you can rest Luigi after he jabs you. You can also rest MK through tornado, I've seen a Ottawa jiggs player rest zaf's mk right through the tornado, for the match.