- I don't think the "trained" boxes are needed. If trained, write in the modifier, which could be "+0". If there is no modifier, consider the skill untrained.
It is still perfectly possible to have a modifier, even a significant modifier, and yet be untrained in the skill.
Trained is reserved for skills you've trained in under character creation -- spent points in (or a few skills are auto-trained by class, like Arcana for mages). It is a special status reserved only for those skills.
And thus, you wouldn't have access to techniques with that skill which require training (such as Acrobatics - Reduce Falling Damage ; Arcana - Identify conjuration/zone/ ritual/ magical effect, detect magic ; Dungeoneering - Aberrant Monter Knowledge )
One could easily have a significant positive modifier in a skill (racial quirk plus attribute bonus plus half-level) without being trained in the skill (it wasn't one of your skills at character creation) -- and as such shouldn't have access to these techniques.
BUT -- that being said ... since you're only going to be trained in a few skills, and there are only a few techniques which require training, perhaps diminishing the "trained boxes" isn't a bad idea? Just little boxes, or pips, or circles, or something? Something small and unobtrusive?
After all, most (almost all) of your skills are untrained, and destined to remain that way. And it only impacts a very few techniques.