You can apply for a J-1 as long as you do not hold any professional pilot qualifications.
I suggest contacting flight schools who do the J-1 and speak to them. They will need to send you the relevant IAP-66 forms before you apply for the visa.
The J-1 is valid for 2 years and there is no maximum amount of hours you can work as a flight instructor during that period.
They may place a 2 year residency restriction on the visa which says that for 2 years after the expiry you cannot re enter the US. This would be unusual though.
Good Luck.
There are many schools which are in the J-1 program.
After spending 2 years over there, I returned to the UK with 1500 hours/500 multi. I would seriously consider it.