On Friday 23rd August, the trains from Exeter are:
Exeter St. David’s departures and Totnes arrivals:

EXD Dep: 09.25 also 09:47 10:12 10:25 10:49 11:16 11:25 etc.
TOT Arr: 10.01 also 10:20 10:43 11:02 11:20 11:47 12:01 etc.

Then walk to nearby Riverside Station (South Devon Railway),
for steam train Riverside to Staverton:

Dep:10.30 11:20 12:10 13:00 etc.
Arr: 10.42 11:32 12:22 13:12 etc.

Tickets for the latter train (required for
Festival entry) can be booked in advance, here:

Rails & Ales info and tickets:
https://www.southdevonrailway.co.uk/visit-us/whats-on/rails-ales/

Main line trains may be quite busy, it being
a Bank Holiday Friday.

There is a decent café in the old Signal Box at Riverside.

Not every train is Steam (see the timetable in the link) and also this info about tickets, taken from the same info page:

Travelling after 18.00? Use discount code ALES24 for 50% the advertised ticket price on single and return tickets!

Our price cap for return fares to Staverton has been held at 2023 rates – only £10 for a return between either Buckfastleigh or Totnes and Staverton – perfect for travel to and from the beer festival.

Entry to Staverton station (and hence to the beer festival) is only possible with an SDR train ticket. For those who are going to the beer festival at Staverton direct and not catching our trains (please remember there is NO public parking at Staverton), you will need to purchase a ticket to enter the station.

PRIV, HRA, SDRA, Disabled/Carer, SDR Shareholder and other applicable discounts are valid on return tickets during this event. They are not available for use with any other offer or discount.