Hello typetre.
You have made good progress and have uncovered some interesting facts and information on your grandfather, Peter Smyth.
He was a member of "D" Co, 4th Battalion, Dublin Brigade and joined in October, 1917
The Tenth Sinn Fein Ard - Fheis was held in the Mansion House on 25 - 26 October 1917, approx 1700 delegates attended, including members from 1009 Sinn Fein Clubs, the approx membership was almost 250,000.
Henry Edward Duke, Chief Secretary for Ireland 1916 - 1918 estimated that Sinn Feins membership was approx 200,000 in October 1917 ( ref - J.E.A.Connell jnr - Dublin in Rebellion )
Your grandfather could have attended and joined the Volunteers at the Ard - Fheis or because his friends had joined.
It was not unusual for volunteers to carry out police and security duties during elections.
If he was on rifle and guard duty at Thomas Ash,s funeral, that would have been a great honour
Not sure what to make of - "Filming of British Collaborations", unless he was carrying out police and security duties.
You should be able to find more information on the Reserve Force in 1941, they asked for old volunteers to join this Defence Force, there should be records on the 26th Batt, if not on your grandfather.
It was also not unusual at the time not to apply for a pension because there was still a deep political divide amongst pro and anti - treaty volunteers, and some may have tried and gave up or they couldn't, be bothered.
Your grandfather, from his records, would have qualified for a pension, I do not think you will ever find out the reason why he didn,t apply, unless there is anyone alive of your relatives you can contact who might be able to shed some light.
You could also look through the posts or enquire for more information on anyone else who had a family member in " D"Co. 4th Battalion, Dublin Brigade.
Good luck
CSM