For bread it'll work just fine, Peter Reinhart's marbled rye bread uses a little shortening in it, and I've seen it in other recipes. You don't even need to melt it (and there are probably reasons not to, according to Peter, he thinks adding shortening instead of oil makes his rye bread lighter), unless you don't know how much you need by weight. If you do melt it, let it cool down a bit.
2.23 cups of crisco (1 pound) melts down to 2 cups of oil, so most recipes just say to substitute measure for measure, if the recipe calls for a half cup of oil, use a half cup of crisco. (I always weigh crisco, though, because you get air pockets when you try to measure it out, a cup is about 7.2 ounces.)
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