Glad to hear your getting back to full health , we are all looking forward to seeing Murphy models grey and Black and Tan 121 class locos visiting Glen More in the coming months .
The coal wagons used on the weekly Foynes -Ballina coal /oil train were older 20’ Tso containers with the roofs cut off re purposed to carry coal painted with grey primer on the inside and black on the outside .
In the late 1990’s the grain was transported in modified 20’ containers from Foynes , Waterford and North Wall to the Conniberry siding in Portlaoise in block trains.
Not to sure what you mean by ‘back to backs’ but they would have carried everything in 20 ‘ TSO , containers , bell , coal , oil , bitumen, asahi, kegs , grain , 10’ uniload , half height wagons , also latterly timber frames .
They would also run as part of Liner trains with bogie 42’ wagons with the two axle wagons marshaled to the rear of the bogie wagons . I seem to remember one of the evening Dublin to Cork Liners possibly the 2040 ex north wall was made up of only two axle wagons all 14’ wheelbase ones up to the mid 1990’s . Should IRM produce one of these this will be a huge gap in the Irish railway modeling scene of the 1970’s 1980’s 1990’ s and early 2000’s covered .
YES , some were repainted in grey .(IRRS journal no 36 Vol 7 Feb 1965 noted B135 being repainted in Grey ) the red buffer may have been an addition to B123 and B127 cant confirm this .
I the early years of the bulk cement they ran with brake van in the train.
http://catalogue.nli.ie/Record/vtls000306218
So you may need to order one of these
Silver , Green and latterly black and tan coaches ran with the grey 121's , the grey livery 121 loco's lasted well into the 1960's I believe, CIE repainted some of them in Grey two in particular B123 and B127 received the addition of a red buffer beam . Would have been nice if one of the grey 121's by Murphy Models had have been B123 or B127 with the red buffer beam but you cant have everything .