I thought about doing that before, but we have no idea how to do a stereo mix or any kind of post mix, that is acceptable for festivals, which is why we hired him.
I can understand not knowing how to do a mix, very few, if any, filmmakers/directors do. However, what I don't understand is not knowing or finding out what it is you need, not hiring someone who can give you what you need and/or not communicating what it is you need! For example, why did you hire someone to do a stereo mix? You do know that there is no such thing as a stereo (2 channel) theatrical mix?
There is no standard film festival specification (either visual or audio specs). Small local festivals tend to screen in ad hoc venues rather than in actual cinemas, in which case a stereo mix is almost certainly what will be needed (both for submission and exhibition). But what levels are required are anyone's guess because ad hoc venues for film festivals are never in my experience calibrated to any standard. If this is the case then a stereo mix to current TV specs is probably the safest choice and is what you should have commissioned. Larger, higher tier festivals screen in actual cinemas, in which case a stereo TV type mix will be required for submission and a 5.1 theatrical mix will be required for exhibition. So before you can hire someone, you need to know exactly what you are hiring them for, what you expect them to create for you AND, the questions they ask you about what you want/need will give you an idea of whether or not they are the right person for the job.
You have also learned a valuable lesson the hard way, which in all fairness is at least partly the fault of the person you hired, because if you negotiated a fixed fee (rather than an hourly/daily rate) then you absolutely must build in an approval process (as has been stated previosly): An agreed amount of additional time included in the fixed fee for you to request changes/revisions before you give final approval. It very much sounds like you have low-balled an audio post fee and hired the wrong person; either someone who had little more idea of audio post than you or someone who thought they could scam you for extra money by not stipulating additional time for revisions.
As AcousticAl and sfoster have told you, with your level of audio post abilities there is very little chance that dropping in new SFX over an existing mix will work, it would be a tricky or even impossible task for someone who really knew what they were doing. sfoster's suggestion of requesting an OMF will not help you much if you don't have any budget for someone to re-mix because the OMF format only includes the tracks, audio clips and may include the panning but will not include any of the processing (EQ, compression, reverb, etc.). You *might* have more luck getting something to work if you request the stems but again with your audio post knowledge the chances are fairly slim.
Your choices appear to be: 1. Stump up the cash for someone who knows what they are doing to do the whole thing again or a re-mix/creative edit if you can get the OMF and/or stems or 2. Trust to the slim chance that your edits will work or 3. Chalk the whole thing up to experience, move on and make damn sure you specify exactly what you need and build in an approval process next time. What I personally would avoid is going back and giving more money to the person who has left you in this situation, as the way you have described it, they have already in effect scammed you once, either deliberately or through ignorance/incompetence.
G
