West System is one of the gold standard makes for doing rowing boat repairs - I at one point was doing all the repairs at a couple of rowing clubs.
Unlike your polyester resin (Upol or similar from Halfords) where the main resin sets at a speed proportional to the amount of the pink catalyst toothpaste stuff added, WS needs to be accurately metered volumetrically Part 1 to part 2 (and there are at least 3 versions of part 2 with different 'going off' times in case of doing repairs in hot or cold weather) - you can get pump kits for this that dose the correct volumes of each per plunge. Get the volumes wrong and it will never set properly, but will leach brown sticky stuff forever more.
Secondly, instead of chopped strand GF mat (which is horrible stuff), consider buying woven glassfibre cloth - this comes in various grades (like any fabric) with varying degrees of coarseness from silk-like (25-30 grammes per square metre) to ordinary building cloth (120-200gsm). If you need it to be really rigid you can get some carbon fibre cloth (200gsm) or similar to add into the laminate. Finally, there is thickening powder - literally glass powder or silica that you mix in to make the resin into a paste for filling purposes. With all of these be aware that it will do horrible things to your lungs so take all sensible precautions.
I used to lay up a laminate of this on either a piece of alu foil or photocopy acetate. If cosmetically important or below the waterline the outermost surface would always be ultrafine cloth to give the smoothest texture. Cut all the pieces of cloth for the laminate (typically 2-3 layers of fine for the exterior surface followed by 2-3 layers of thicker cloth for the repair strength) using clean and dry good quality scissors. Then, put the first piece onto the foil / plastic surface and pour some mixed resin onto the centre of the cloth. Using wooden coffee stir-sticks I would then work the resin out to the edges in smooth movements fully wetting the cloth but eliminating all excess. Then lay on the second layer, possibly with the weave at a slight angle to the original, and again work the stick from inside to out to wet up the layer completely. Use the stick to add a bit of resin from the edge to the centre and repeat with the next layer. Once all layers added I would then also wet the area that the patch is going onto (having already cleaned, sanded and prepared this a suitable distance from the hole or crack being fixed). Using the "wet scissors" (a pair only used for cutting laminates), then cut the patch to a clean shape removing the uneven laminate edges (where there is excess resin, loose strands and uneven layers of cloth) then invert and lay the patch onto the surface, using gloved fingers or a teflon roller to apply pressure from the middle outwards to avoid bubbles or wrinkles. FInally, peel off the foil / acetate layer by hooking a corner and then peeling it back very closely on itself so as not to pull the laminate off the surface, and leave the patch in situ to polymerise in place.
Once fully set, it was then a case of sanding back using fine and finer papers, then using filler primer to bring up the surface and primer paint to cover over, then fine sanding until the surface was ready for top coat, but obviously less necessary on the reverse side.
