What are the easiest Sharia-compliant solutions available for the problem of drops of urine or water used for purification (istinja’) exiting after purification, and do prayers become invalid because of that, and does one fall under the warning mentioned in the noble Hadith: "Cleanse yourselves of urine, for indeed, most of the torment of the grave is due to it"?

If the feeling of something exiting after performing istinja (washing after relieving oneself) is merely a doubt or a whisper [from Satan], do not pay attention to it. However, if you are certain that something has exited, then purification from it is obligatory. Maliki jurists make it easy in this regard if it occurs daily. Wudu (ablution) becomes obligatory after the cessation of this discharge, and then one may pray.