Sealing a V8 sump

Mine's been leaking since I rebuilt the engine, I was rushing to get it finished at the time.

Anyway, finally got round to sorting it today so I've got the sump off and it's nice and clean but it's very difficult to slot it back without catching things on the way which could dislodge some sealant.

Has anybody tried letting the sealant go off before re-fitting? Did it work?

Also, recommended sealants please.

Thanks

it dont work.