The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) writes in Parashat Debarim (listen to audio recording for precise citation) that one should make a special effort to recite Birkat Ha’lebana on Mosa’eh Tisha B’Ab with joy. Birkat Ha’lebana should always be recited joyfully, but this is especially important on Mosa’eh Tisha B’Ab. In particular, one should recite the verse of "David Melech Yisrael" with special feelings of joy, as this verse relates to the theme of Ge’ula (redemption), which of course should be at the forefront of our minds as we leave Tisha B’Ab.
A number of Halachic authorities raise the question of whether Birkat Ha’lebana may be recited with non-leather shoes. This recitation involves the greeting of the Shechina, and it should therefore be recited with fine clothing. Perhaps, then, it should be preferable to first return home and change into ordinary shoes before reciting this Beracha. However, the Mishna Berura (Rav Yisrael Meir Kagan of Radin, 1839-1933) writes (426:11) that if the congregation will be reciting Birkat Ha’lebana together after Arbit, it is preferable to recite Birkat He’lebana with the congregation, "Be’rob Am" (with a large crowd), even in non-leather shoes. But if, for whatever reason, one will be reciting Birkat Ha’lebana privately, and not with a Minyan, then he should first put on his leather shoes before reciting the Beracha.
Another issue is whether one should first break the fast before reciting Birkat Ha’lebana, so that he will be able to recite it with joy. The Hesed La’alafim (Rav Eliezer Papo, 1786-1827) writes that it is indeed proper to eat something before reciting Birkat Ha’lebana on Mosa’eh Tisha Bab. However, the consensus among the Halachic authorities is that it is preferable to recite Birkat Ha’lebana with the congregation without eating, than to return home, eat and recite the Beracha privately. But if one will in any event be reciting Birkat Ha’lebana privately, then he should eat something before reciting the Beracha.
Summary: It is customary to recite Birkat Ha’lebana immediately after Tisha B’Ab, and it should be recited joyfully. If, for whatever reason, one will be reciting Birkat Ha’lebana on Mosa’eh Tisha B’Ab privately, then he should first break his fast and put on ordinary shoes. Preferably, though, Birkat Ha’lebana should be recited together with the congregation, even with non-leather shoes and even if this requires reciting the Beracha before breaking the fast.
