Answer
Do not sand soft caulk. Let it cure, then sand only adjacent hard paint edges with 220 or 320 if needed.
Why it happens
Flexible caulk is not meant to be sanded like filler; sanding can tear or smear it.
Recommended grit
Do not sand soft caulk. Sand only adjacent hard paint edges with 220 or 320 after caulk cures.
Wet or dry
Dry.
Success check
The caulk is cured and surrounding paint edges are smooth before coating.
What to do
- Let caulk cure fully before painting.
- Do not sand the soft caulk bead.
- Sand adjacent hard paint edges with 220 or 320 if needed.
- Remove dust before painting.
Avoid: Do not sand uncured or flexible caulk directly.