Watch out for the silicone, some brands don't age well, and you won't be using a lot of it.
I learned my lesson the hard way, had to throw away a half of a 5kg bucket.
Resins are sensitive to moisture, ESPECIALLY polyurethanes. Limit their exposure to air humidity. Don't keep the containers open unnecessarily. Spray them with lighter butane, canned air, or CO2 just before closing the container. Those gasses are heavier than air, they'll displace it in the container, limiting amount of air humidity that could come into contact with the resin during storage.
Keep them away from high temperatures. Store them in a ventilated area. Especially the polyurethanes, because of isocyanate sensitization (look that up).
In general, calculate your batch sizes, timelines, match them to order volumes, and try to use up your stuff quickly. Do as little storage as comfortably possible.
For mixing, I suggest calculating the volume from mass/density (check datasheets), and doing volume based mixing, unless you're comfortable with shelling out north of $300 for a good grade used laboratory scale. Measuring by weight is more accurate only if you have a precise scale, and they don't come cheaply.
I suggest using math+physics and syringes instead.
I kinda wish there was something like a giant refillable caulking gun for the silicone.
There you go.The general practice to keep them clean is to use a foil bag. Put it inside, and pour the silicone into it.
If you have a compressor, there are pneumatic versions as well, they do the squeezing for you.
You can also get a pressure paint container with a bottom drain, pour the silicone in, clamp a valve on a hose, pressure it up, and you're good to go. Make sure you have a dehumidifier, or use preconditioned gas (like CO2 bottles).
What used to work for me in the past was to store the silicone in plastic bottles (think coke/pepsi) upside down. Open the cap, squeeze out as needed.
Have fun!
