Painting demonstrations are generally planned to fit into the typical 2 hour meeting time of most art groups. Allowance is made for introductions, notices, tea break and discussion.
Specific techniques and subject matter can be arranged to meet the needs of the group.
Examples of previous demonstration pieces are shown on this page.
My basic fees for such sessions (for 2018) are £45 per hour plus travel costs from my base in Doncaster, South Yorkshire.