I can't lose (Unfortunately)

[Statutory]

A few months ago I purchased the following index funds on Vangaurd:

Vangaurd 500
Vangaurd Pacific
Vangaurd European


I spread my money around hoping to take advantage of the 3k/year deduction from losses, all are up, which is clearly great, but I'd like to set myself up for any and all tax benefits.

SO my question is, I am going to buy more index funds. IF I buy into the same index funds, and they go down, can I sell specifically the shares I lost money on? OR is there cost averaging or some other method of not letting me take a loss. Then I should by in different funds I suppose?

And I would still love an answer to my question about whether investing in foreign index funds hedges or bets against the US dollar?

Thanks