[34C]

Likewise, solder pastes are very useful.

But for use in temporarily bridging baseboard joins by the method described, you might as well use resin cored electrical solder. (Advisable to have available at an exhibition for inevitable running repairs.)

And that's only if you choose this method for baseboard joints. What's wrong with a joint system that robustly and stably secures alignment of the base boards, which means that the track ends must align over the join? Soldered track won't prevent baseboard ends moving out of alignment if the baseboards are not stable. Think temperature variation, floor movement, 'nudges' from the viewers (watch the two metre tall 150kg man pass out and hit your layout on the way down - an event I witnessed!).

 

[34C]

Good to see the layout is modest in size, that does reduce the problem set. The dowels and bolts should be enough to do the job of rail end alignments, even though oblique. (Probably teaching grandma to suck eggs , but assemble baseboards with 0.5 mm shim in joints, lay track, soldering what will be rail ends to brass screw heads at board edges, cut through rails over join using a razor saw, dismantle layout, remove shims, reassemble, perfect!)

All the best with exhibiting, and please report on the experience of using the aligners.