[tabletop epoxy brain dump]
Most of the tabletop epoxies are just high clarity epoxy chemistries, and are lower cost chemistries so they're fairly affordable ($60/gallon or whatever is pretty cheap for epoxy), but are have relatively low physical properties.
The coating thickness recommendations are to make it easy to get bubbles out, and also to control exotherm (heat release) during curing. Slower setting epoxies can be cast in greater thicknesses because the exotherm is lower and easier to control, and ambient temperature affects that as well (cold air, cold epoxy, cold materials, etc). Materials that conduct heat will also allow greater pour thicknesses, instead of materials that are good thermal insulators like wood. Basically, thickness is a recommendation and not an absolute.
Follow the instructions about time between pours, because waiting too long between consecutive pours could make problems with optical clarity and prevent proper crosslinking between coats (waiting too long can cause imperfect results, basically). Most of these products are formulated to be pretty foolproof, so that's a plus.
Following mixing ratios is important too, but again they are formulated to be semi-foolproof so there is a fudge factor for volume ratio. Get graduated mixing cups, like the ones used for mixing automotive paint.
Do at least one small test batch and let it cure fully, because you want to make sure that your method for measuring and your method for mixing the components together are both effective
before actually pouring epoxy onto something important.
I use a cheap heat gun for bubbles, because it makes a lot of heat without a lot of airflow, which generally works better than a hair dryer. The people that do epoxy pouring a lot will often vacuum de-gas the epoxy before pouring, but that requires a vac chamber and a vacuum pump. Gets rid of a lot of headaches though, if you're frequently pouring a lot of epoxy. Following recommendations for waiting a certain amount of time after mixing (before pouring) can also help control bubbles, as you can let them settle out in the mixing cup instead of in the work piece.
You can only effectively get down to a certain depth to get out bubbles when using a heat gun, which again is one of the reasons that most epoxies don't recommend a very thick pour at once.
Epoxy viscosity has a lot to do with trapped bubbles as well, for obvious reasons. Think of bubbles in water versus bubbles in honey, etc.
I actually have a lot of fun playing with those types of epoxies, because they're waaaaay easier to use (and cheaper) than the epoxy adhesives and coatings I usually play with at work and while doing composites projects. Sometimes it's just fun to mix two things together and do something cool with it, without turning it into a scientific process and getting out scales for ratio measurement.
This stuff is actually easy to use, I just want you to know
why the instructions tell you to do something. It's always better that way, instead of blindly following instructions and thinking "well, they told me to do it this way, and they must have a reason for it"...
Some people may already know that I'm a little bit of an adhesives nerd....
[/tabletop epoxy brain dump]
