Press and seal is rarely necessary, I have never used it.
When you have eggs if you do it sooner the moisture contained in the hatchrite will be gone, also since you are using a substrateless method I would just go with a cheaper medium.
Hatchrite is technically fool proof for those who do not want to mix anything, which is the principle of the substrateless method as well allowing you to use a cheaper medium such as perlite or vermiculite.
As for thermometer get a thermometer/hygrometer which will show humidity as well.