This article describes improved measurements by CLEO of the B0→Ds+D*- and B0→Ds*+D*- branching fractions, and first evidence for the decay B+→Ds(*)+D̄** 0, where D̄**0 represents the sum of the D̄1(2420)0, D̄2*(2460)0, and D̄1(j = 1/2)0 L = 1 charm meson states. Also reported is the first measurement of the Ds*+ polarization in the decay B0→Ds*+D*-. A partial reconstruction technique, employing only the fully reconstructed Ds+ and slow pion πs- from the D*-→D̄0πs- decay, enhances sensitivity. The observed branching fractions are B(B0→Ds+D*-) = (1.10±0.18±0.10±0.28)%, B(B0→Ds*+D*-) = (1.82±0.37±0.24 ±0.46)% , and B(B+→Ds(*) +D̄**0) = (2.73±0.78±0.48±0.68)%, where the first error is statistical, the second systematic, and the third is the uncertainty in the Ds+→φπ+ branching fraction. The measured Ds*+ longitudinal polarization, ΓL/Γ = (50.6±13.9±3.6)%, is consistent with the factorization prediction of 54%.
