I just use a small food style vac sealer. The tek i use is just to hold down the vac button until the buds start to squish, then let go of the vac button and push the heat sealing button. In the split second between letting go of the vac and the heat sealer getting up to temperature, there is a bit of vac released on the bag before it is sealed shut. That split second stops the buds from being squished together with too much force.
The buds need to lose their tackiness before sealing. If you cure them in a room with 58-62% humidity for about a week the trichomes become less sticky and store better; it’s like letting the glazing on a donut firm up before putting it in the box.
I’ve definitely had my fair share of bricks form! Usually, after bucking and before the dry trim, they’ll turn into a brick if I don’t let them develop that exterior of firm trichomes before they go into a bucket or bag.