Superconducting oxides like other materials, display intermingled microscopic ("ideal") and mesoscopic (usually sample-dependent) properties. By describing quantitatively the resistive transition we show that each contribution can be understood separately. A very simple grain-barrier model, together with the idea of a two-step superconducting transition and well-known theories of fluctuations in superconductors are the ingredients of this description. We thus identify the ideal critical temperature Tcs , even in degraded samples. Similarly other microscopic parameters like the coherence length in the c-direction and the distance between CuO2 planes, in good agreement with the crystallographic data, are obtained without adjustment from purely resistive measurements at T > Tcs .The relevant sample-dependent quantity is the barrier contribution to the total resistivity, and is obtained from measurements at T < Tcs . Finally, we discuss critical current measurements, and show that different behaviours, related to grain size and coupling, can be expected.