OK, so have a pair of 50mm carbon tubs and after fitting the rear tyre the rim had a knock - before it had got close to being on a bike 
So rim went of for repair, refinishing, and now all is good... that said I have just put the second coat of tub cement onto the rim, and so am close to being able to refit the tubular tyre...
This is where the problem comes in. The tub, new but put on and removed whilst the rim was refinished, has a layer of glue on the fabric. This is naturally a bit patchy in condition.
Do I "sand" it back? Do I simply build up fresh over the old? Do I have to pick all the glue off the fabric and start from clean?
Any advice would be great, dont really want to bin a £45 tyre that hasnt been ridden.
Cheers for any help
Johnny

So rim went of for repair, refinishing, and now all is good... that said I have just put the second coat of tub cement onto the rim, and so am close to being able to refit the tubular tyre...
This is where the problem comes in. The tub, new but put on and removed whilst the rim was refinished, has a layer of glue on the fabric. This is naturally a bit patchy in condition.
Do I "sand" it back? Do I simply build up fresh over the old? Do I have to pick all the glue off the fabric and start from clean?
Any advice would be great, dont really want to bin a £45 tyre that hasnt been ridden.
Cheers for any help
Johnny