Was/were is used with a present participle (-ing form of a verb) to create the past progressive.
Used is the past participle; using is the present participle.
The present participle is the -ing form of a verb.eg using walking talking listening
The present and past particle of the butterfly is butterflies. butterfly is a noun and doesn't have a present and past participle
The present tense of used is:I/You/We/They use.He/She/It uses.The present participle is using.
Being is the present participle. The past participle is been.
Getting is the present participle of get.
The present participle is doing.
Presenting is the present participle of present.
Presenting is the present participle of present.
The present participle is choosing.
The present participle is walking.
The present participle is cleaning.