Calculating effect size with interaction term

#1
If I am running multiple regression in r, what is the next step in order to get the effect size for all variables when there's also an interaction term in the equation. For example:
model=lm(DV ~ Var1 + Var2 + Var2:Var3)

Also, what's the best way to determine whether or not to do an interaction analysis if there are many dependent variables, making the creation of a bunch of plots a bit tedious…

Thanks!