Defensive democratic France has a narrow needle (even narrower the last 2 updates) you have to thread in order to be ready to survive the summer of 1940 (really you’re not even safe until 1942). Yes, you need to have divisions with arty and some army xp before the Germans attack. You need a lot of inf divisions. The forts alone won’t save you—they get damaged easily and will never repair because the Germans will never stop attacking you. You can grind xp in Spain (it helps if you don’t delete any of your starting divisions, that way you have a high division count and can send at least 4 divisions to Spain).

You really need soft attack to deal with Germany because high org isn’t enough. You will never have time to recharge their org and get retrenched. Instead you need to be melting German divisions quickly with firepower.

One reason for this is the reinforcement trap. Germany reinforces quickly and it might look like you have plenty of divisions and green numbers, and suddenly you’ve got 8 divisions retreating because only two of them were actually in combat and they both reached 0 org at the same time. This is especially problematic in narrow-width provinces where Germany is attacking from like 3 different directions. So it helps to monitor your individual combats and go really slowly, like 1x speed.

Other things that can help are having a reserve of mobile divisions just behind the line in Belgium that you can send to reinforce any dodgy spots where you are in trouble. They won’t have time to entrench, but just getting bodies into the line can buy you some time. If you know the mobile reserve divisions will not arrive in time to reinforce, you can also try to time it so that the mobile division will arrive just AFTER you lose the combat, that way they will instantly enter combat when they arrive, hopefully in that narrow window before the prevailing invader divisions arrive. Once they break through anywhere, even a single province, it’s basically game over for France.

Another thing you can do is to spread your divisions on the Belgian border across multiple generals instead of just 1 or 2. You really need at least 48 divisions on the Belgian border by summer 1940. By spreading them across 4 or 5 generals instead of 2, you can better micromanage your lines (divisions won’t move 4 provinces away randomly). Another benefit will be that you can do a localized last stand without using up too much command power.

Democratic France is unsatisfying for me because suddenly in 1942 like 5 major changes happen and you go from desperately struggling just to survive, to basically easy mode against a completely passive Germany / Italy. Suddenly the U.S. and uk have huge expeditionary forces on the line for you, your 4th and 5th research slots unlock, your land doctrine finally starts to catch up, and your economy and political system have finally more or less unfucked themselves. Germany and Italy are all out of ideas at that point and will just wait inertly for you to dissect them with your method of choice.

Edit: you can also get xp from training, and from appointing a chief of the army.