Based on s.m.'s answer it seems you can combine EACH() with both .key and .value to generate columns automatically.
Setup test table like in Ian Timothy's answer:
create table hstore_test (id serial, hstore_col hstore);
insert into hstore_test (hstore_col) values ('key1=>val11, key2=>val12, key3=>val13'), ('key1=>val21, key2=>val22');