Tendo visto o filme duas vezes, posso certamente confirmar que
the Soul Stone was used to animate the rock fragments on Titan that became bat-like creatures that were "thrown" (better, directed) to Iron Man. If you watch closely, Soul Stone enlightens and moments later you can hear the rustles of the animated "creatures" flying to Tony.
Quanto a
the Mind Stone,
podemos assumir que ele foi usado para
gain knowledge on how to heal the wound Thor caused using the Stormbreaker, as Thanos is seen unharmed at the end of Infinity War, when he stares at the sunset. Unless Thanos possesses healing powers, no other Stone -except maybe for the Time Stone- can heal someone, albeit indirectly.
Além disso,
all six Stones combined were used to wipe out 50% of all life on the universe. So, even if my previous assumption is wrong, Mind Stone was used alongside the other five Stones, for Thanos's greater plan.