Two different methods for detection of the transient absorption (TA) and stimulated emission (SE) by using a two-step excitation thermal grating technique are characterized. The sensitivity and the temporal profile of the signals are analyzed in detail. One of them, prepulse-(delay)-grating pulse sequence, provides a very sensitive TA detection with a zero background. The other one, grating pulses-(delay)-boosting pulse sequence, has also a very high sensitivity for the detection of TA and SE together with an easy probe wavelength scanning. The high sensitivity of these methods comes from the cyclic excitation of the excited state and accumulation of the thermal energy. These methods are used to measure the T-1-T-n absorption spectrum of benzophenone, and the T-1-T-n absorption and SE spectra of rhodamine 6G.