Changes

If you just want to get to Portugal, you'll want to to keep your hitch journey in Spain as short and quick as possible. This will happen by sticking to the the main road (AP-1, A-62, mostly "autovia") from Bayonne/San Sebastian to Salamanca / Vilar Formoso (the portuguese border near Guarda). Even if you come from, say, Montpellier, it's recommended to hitch up to Bayonne and cross the basque country.

A good technique is to stay in one of the last service stations on the A63 in France before the spanish border, and wait for someone who can take you all to way to Portugal. Portuguese plates (1/3 of portuguese nationals live outside Portugal) or tourists (20 million invaded Portugal in 2016) will pass there.

Otherwise, don't let your drivers drop you at just any gas station along the way - try your best to stick to busy ones (on the right side and near the highway, Repsol and Galp).

If your ride is only taking you to somewhere near Vilar Formoso border and you want to go further in Portugal, you can stay at the last Cepsa gas station on the right side of the road, 5kms before the border. Gas is cheaper in Spain.