Charging there's a ton of ways. If you just press 4 instead of hold it you can recover almost instantly. This catches people off guard and you can basically use it as a bait. It also allows you to use it in combos off of AAs or during regular 1 bar combos. And if you really need trait you can just end a combo in b232 or charge a full bar after MB Freeze (and if you learn the timing you can charge and then still get free pressure when they unfreeze).
You can essentially use it whenever, but its probably best used to extend combos for more damage/corner carry or after b232 since they'll be stuck. Once they're stuck in the ice field you can stay in AA range and chuck projectiles or you can go in and abuse the slowdown for much better pressure. If they're smart they'll probably just backdash out of the field, so if you have meter it can be pretty dirty to use EX far icicle and then trait, which means they essentially have to come to you.
That's just week one stuff obviously. Sky's the limit with his trait and Its very likely people will come up with more optimal stuff down the road.