Why would Portugal "sit it out?"
Salazar's government won't survive a transatlantic naval blockade, nor a Francoist invasion either.
Only one neutral country on the Iberian peninsular got large numbers of advanced combat aircraft from its Allies (142 Hurricanes, 105 Spitfires, 20 Airacobras, 20 Blenheims) during WW2 and it wasn't Spain.
Spain is going to be massively reliant on German and Italian support from the outset, given their trade with the USA and Mexico just evaporated.
Given Italy was reliant on the Reich, it's just chucking worse money after bad money.