Are your brake shoes worn - they may need replaced, if OK then check the self adjuster mechanism is working so that the shoes are correctly spaced in relation to the drum. Otherwise maybe the drums are worn.
Hummm, my hand brake was sticking a few months ago, the problem then went away and now the hand brake doesn't work unless u really pull it on hard then seems fine. Passed its MOT yesterday tho so guess they must see it as safe. I always leave it in gear and avoid steep hills to be sure
Something I learned from the past (51 years) is that I always use (except in wintertime) the handbrakes, this to avoid the sticking or bad functioning of one of the parts of it, when used regularly it has tendency to keep working ok.