A couple questions about holy water

[Daniel]

I understand that holy water is a sacramental so it has power to forgive venial sins iff the person using it is contrite. And if I remember correctly, there's also an indulgence for using it piously.
But I was wondering about people who are in the state of mortal sin. If such a person were to use it (contritely and piously) would his venial sins be forgiven? And would he be able to obtain an indulgence (for the dead) in this manner? Or would his lack of grace completely cancel everything out?

I was also wondering about the asperges ceremony at the beginning of the High Mass. So, the priest sprinkles the congregation with the water in order to cleanse their sin. But clearly the water does not make physical contact every individual in the congregation. So how does that work? Is only the congregation's collective guilt forgiven (rather than the guilt of the individuals in the congregation)? Or is the personal guilt of each individual in that congregation forgiven as well? Or does it only have an effect on the individuals with whom the water physically makes contact?

[Gardener]

Venial sins cannot be forgiven by use of holy water when in mortal sin, lest an act of perfect contrition takes place. That would be like someone's sickness being cured when they are in fact dead.

If one appears to make and intends to make an act of charity, they are either not in mortal sin or they are doing something by habit without the concurrent grace to affect it.

Yes, the Asperges would have an affect on all, even if a drop of holy water did not touch a person, assuming the usual conditions. Just like when a priest does a mass blessing of sacramentals, it is not necessary that holy water touch everything as the individual parts are included in the whole.

[Daniel]

I see. That makes sense, thanks.

[Kaesekopf]

The Asperges question answers part of what I usually ask myself on Sunday mornings.