You can just head to the train (or commonly to the access checks). They will look at them weirdly (as they have no barcode nor a reference number they can look up) but should accept them. 

The on-board conductor actually used the seat map on his PDA to check the tickets, as he had no other way of localizing them (the ticket number printed on them can't be found by Renfe staff either), but as they're printed on secured paper they should know its genuine.

Can you reliably get RENFE seat reservations in the DB app or is it only on paper? That’s great! How do you get them?

As far as I know, you can't use the DB app for reservations. But I had absolutely no problem getting the reservations at the ticket counter in the train station.

Thanks, I’ll try the NS International counter here in Amsterdam and see if it’s possible there. I’m crossing Spain in March to go to a meeting in Portugal. I’m planning to go (Amsterdam → Brussels → Valence → ) Barcelona → Madrid → Sevilla → Huelva → Ayamonte (the last bit by local bus), cross into Portugal on the little ferry and then take the train to Faro.

I haven’t even been able to get regular tickets Barcelona → Huelva from the RENFE website (you have to break the journey into separate Barcelona → Madrid, Madrid → Sevilla and Sevilla → Huelva sections), so being able to get an Interrail ticket and reserve from here would be great. 

I think you can indeed only get them as paper tickets, so either at a ticket office, getting them by postal mail (€5.90 delivery fee I think) or by calling DB and collecting them from a DB ticket machine (there is also one DB ticket machine in The Netherlands, in Enschede)

As far as I know, NS is not able to book them, but you can always try. 

Nice route indeed! Madrid-Huelva has at least one daily direct Alvia (which should avoid Seville), but there are indeed no trains from Barcelona. 

Renfe only offers trips involving multiple trains that have been manually programmed, but otherwise they tell you to find it out yourself. The DB planner is helpful but not always complete (as Renfe doesn't always provide the data on time). 

Just also read that many more local RE etc trenes CAN only be RES till some 4-5 weeks ahead-and if even RENFE cannot do it, how on earth could also the germans or dutch? ONLY AVE/Avant=the hi-speed on the normal rails (not the old style wide) mostly tend to have a bit longer in advance. It seems about anyone know gets the stress if the whole trip cannot be fixed many moons ahead.

Double check if that route via ferry is stil doable_I also did it once, other way, I recall having read there are now probs with the ferry or whatever. There are also 2-3 /day (more often in main season) direct BUSes Svl_Faro, also usable for shorter segments. As there is since my trip now a new bridge that has taken much loads off that ferry.

For DB: it often helps if you can give them the train nr, look that by yourself in the RENFE site

RENFE DOES offer 2 trenes directo desde Bcn a Cordoba-where they split to Svl and/or Granada or Malaga-but these seem notorious hard to get seats on with pass. Cuts of the in+out of MAD and saves some 1 hr.

Indeed. Do let us know if NS can book them since that would be a useful addition.

I’ve traveled in Spain and just did my reservations at the stations 1 of 2 days in advance. Never had any problem. Reg.Exp. trains are free (without reservations) to use is my experience. A bit slower but mostly the routes are nice ;-)

This evening I popped up to the NS International ticket desk at Amsterdam’s Centraal Station (and admired the amazing new underground bike parking for 11,000 bikes on the way in). 

The person who helped me (who was very enthusiastic and knowledgeable) said that NS can only reserve to Barcelona with their booking system, but the whole RENFE booking service isn’t connected to theirs. She was aware that DB is connected to RENFE, but said Spain has always been a problem for NS - they can reserve/purchase pretty much anywhere in Europe, but not Spain.

Her advice was either to call DB, SNCB or SNCF, or to find someone in Spain who could make the reservations for me.