Unless things have changed a lot, instructing in France with a JAR licence not issued by the french authorities is not an easy thing to achieve, they try to protect their job market, unfair but it is the way it is .
In short, there are very few paid FI jobs in France, most of the instructing at PPL level is done at aeroclubs , which are non profit organizations, and most of their instructors are not paid (the background varies from the military pilots instructing for fun on their free time,to hour building young CPLīs, or experienced PPLīs).
There are over 500 aeroclubs around the country, quite a lot of PPLīs around.
Of course your French has to be up to scratch.
Unless you have an special interest in working there, it is not worth the effort, since getting a paid FI job is quite hard.
As far as I know you could instruct in Spain without having to do any request or paperwork to the spanish authorities,
AFAIK the same applies to Portugal.
The problem in Spain is finding a job, even more now, because of the economic situation.
Unlike in UK or France, the GA industry is very small, very few PPLīs train every year, so not many jobs around.
LEVC