you got 8x3 from waterbury correct? then use 85% of you're 1rm and short rest intervals between sets, like 70 sec. Its not suppose to kill you. i did 10x3 with 85% of my 1rm, no problem, but you get gains. but dont do 8x3 for all days as its alot of sets and you would end up fatiguing you're self, either one of you're training days (if you do fullbody) or do them for chest one day, back one day and legs one day (just an example)
I had great gains from this method.