I would add an air dry or warm air dry after the IPA rinse to evaporate any residual or absorbed IPA, No more than about 40 deg C. for 30 to 40 mins.
Don’t forget to give the resin a good agitation before use, There is a lot of dense filler in the resin and it can settle out. I rock my resin cartridges from side to side for 10 mins with the screw top and bite valve at the top so there is no chance of the resin splashing out!!
If you leave your resin in the tray, again agitate to get the filler mixed in. I use a silicone spatula.
Smoothon Sorta clear 18A is quite forgiving, but follow their recommendations exactly ie weigh accurately, mix, pour into new mix cup and mix again. If you don’t want bubble you will need to degas. I have some clients who had “sticky” silicone and it was because they had not mixed their silicone thoroughly and the other reason was they were using latex gloves.
Our moulds are tiny and we mix only 30ml of silicone at a time so any bubble will fail our moulding.
Some people like brushing the silicone into the mould to wet the mould surface before pouring. We don’t as it is an extra process and we will get through a fortune in disposable brushes! We actually inject our silicone at high pressure.
Without seeing your mould I cant advise.
I never use heat on my moulds as this distorts the mould and secondly it affects the shrinkage rate of the silicone.
I don’t use any form of barrier as it may affect the later processes when we bond to the silicone.
Your UV cure time seems long, but it will be dependant on your UV out put power and frequency distribution (405nm??) there are many good blogs on this forum on uv cure. Most of my know how came from there then I added the science!
Good luck and let me know how you get on.