Six-letter words - change zero to two letters make a new word (Part 1)

sashay

Shazam!

Hamish

Masher

warmth

swarms

smarmy

summer

muscle

Cletus

Oompah

Oompah? I can’t figure out which word that would follow.

subtle!

Erebus

bruise

busted

steady

tasted

jetted

vetted