It is quite possible to vacuum bag polyester/glass laminates, but there are a few things that you must look at to determine if it's practical for your application.

The vacuum bag process brings atmospheric pressure to bear evenly on the curing laminate but applies no load to the mould so that excess resin is squeezed out and, usually, soaked up in a disposable outer wrap. This technique requires a vacuum bag and a vacuum pump capable of pulling a significant vacuum (at least 25 inches of mercury), and various accessories and supplies. You should allow for the cost of the vacuum bagging equipment, materials (pre-release film, peel ply, breather, vacuum bags, mastic tape, vacuum pump etc.,) and extra labour as you will have to finish a complete layer, or two, before the bagging can be applied. This means that you will have to be using a slow cure, low exotherm resin. To offset this added cost, with the correct vacuum, you will gain the advantages of a near perfect resin/glass ratio and have any fumes extracted from the laminate and ejected via the vacuum pump. Until now vacuum bagging has been mostly restricted to commercial use and a few enterprising owner builders.

   Vacuum bagging epoxy laminates is more common as the cure is slower and the strength/weight ratio, usually, more critical. With polyester/glass laminates, it is more usual to use vacuum bagging on the core (dry bagging) rather than on a solid fibreglass laminate. Vacuum bagging allows cores to be bonded in place with minimal amounts of adhesive. When you compress fiberglass under vacuum, you can loose up to 30% of the thickness, which will greatly decrease the stiffness so coring the laminate may be the only way to go.

   Your materials suppliers should be able to supply most of the equipment and advice that you will need for vacuum bagging or tell you where to get it and, possibly, advise where you can see the technique in operation.