I recently picked up a pretty complete (to my eye) cast your own resin parts kit. Anyone have experience using these kits to produce the odd bits of storage -jerry cans, packs, etc Any hints or advice, pitfalls you learned the hardway that can be avoided? I’m not trying to fab conversions but at times it would be nice to have that extra pack, duffel, crate etc. I hijacked some of my daughters lego’s to build the mold walls for the rubber molds you start with, any advice on what the max workable size would be and optimal number of parts in a particular mold before you start affecting the durability and viability (for instance stick to 6x6 inch squares w only a 1/2 dozen parts etc). Any and all insights welcome and desired.
I discovered that the 2 part resin sets a lot fast than it used to 10-15 years ago.
there are plenty of videos on YouTube which will be of use.
FWIW - here’s my .02 cents worth…
If the part is available in the aftermarket buy there instead of doing your own resin casting. Reasons being, it’s expensive to do correctly by the time the chemicals, mixing items, mold materials and a vacuum chamber are acquired. Great Ventilation and a high quality respirator are needed in my opinion.
It’s a lot if time and resources that could go into something else never mind the health risks.
If you have much of a quality standard the yield will likely be terrible without a vacuum chamber. For an old Panzer IV kit, I did some resin casting basically copying the radio and driver hatch bullet splash rails with attachment points. The parts were a 1mm in height, 4 mm long & 8mm wide hollow and very thin. Nothing aftermarket was really available to meet the need at the time. My yield for quality parts ie no air bubble or other defect was about 20 percent. I didn’t have a vacuum chamber. 
Doing the front & rear fenders was even worst, probably a 10 percent yield.
It was time intensive to get two quality sets of fully detailed bullet splash rails, two rear fenders & two front fenders. It was ultimately worth doing as it was the only way to wrap that particular project. However, I have no desire to ever resin cast anything again.
Those silly tan colored rails around the driver and radio operator hatch and front fenders below
