In less than 24h, some1 updated his downgrader to be compatible with all PSP models. People with a 07g or a 09g will be able to downgrade to 6.35, while others can go down to 6.20. This will let you install either TN’s Hen, or CFW Pro
If you have anything lower than an 07g place the 6.20 update in PSP/GAME/UPDATE.
If you have an 07g or an 09g, place the 6.35 update in PSP/GAME/UPDATE.
You can get the updated downgrader here
You will also need the official PSP OFW 6.20 or 6.35 depending on your model: