In general, the participle resembles the 3rd person plural without the -इ: √गम् → गच्छन्ति → गच्छन्त् / गच्छन्ती
Masculine and Neuter: add -अन्त् to the weak present stem: √भू → भवन्त्; √कृ → कुर्वन्त्; √अस् → सन्त् exception: for class 3, add -अत् to the weak present stem: √भी → बिभ्यत्
Feminine: add -अन्ती/-अति to the weak present stem: -अन्ती for gaṇas 1, 4, 10, usually 6, and single-syllable roots in 2. -अति for all other gaṇas.
Masculine nominative singular does not lengthen final vowel: √गम् → गच्छन्; √भू → भवन्; √आप् → आप्नुवन्