The co-thinness of sets is studied by means of $h$-processes. Co-thin sets are characterized by a balayage property and are semipolar sets. The method avoids the use of time reversal.
"Quelques Ensembles Exceptionnels En Theorie Du Potentiel." Ann. Probab. 6 (2) 316 - 320, April, 1978. https://doi.org/10.1214/aop/1176995575