have not gotten an opportunity to actually use techniloom yet, not much i can say there. defensively speaking, breloom has the ability (poison heal is just superb) and it has the typing (edgequake/water/electric resist is awesome), but the movepool is only so-so from a stall standpoint (spore and leech seed are the only things that stand out, and the 4mss is crazy if you run them both), and the stats are atrocious (breloom has like only ONE usable stat, which is its attack). tough to use it in that way, if at all.
i spent a long long time theorizing about the bulk up set because i wanted it to work on my stall team, but every time i try to use it, it just does not pan out. it shines against precisely one type of team: rain stall (and that's assuming the bulky waters aren't carrying ice beam or roar x_x), since it can set up on any mono-attacking bulky water (eat scald and volt switch for breakfast) and can also set up all day long on ferrothorn. in theory it should do fine against most such mons. but it really doesn't have the room to be effective right now - it's way too easy to check (slow as shit, and no mach punch), and it's too difficult to get set up unless your opp makes a mistake. i hate ferrothorn's guts so for a while i was running it anyway, but i only ever got set up once, which was when my opponent made a mistake and tried to beat me up with an ice fang/eq uninvested gliscor - instead i bulked up and got enough boosts that he could no longer switch in on me. but that was once. ONCE.
i have not gotten the opportunity to test substitute loom (probably a specially defensive subpunch is what i'd end up running) but in theory it should fare better right now - if you do manage to force a switch, sub at least lets you deal a hit before you get forced out, and substitute is always useful for mons that are easily checked. where as if you bulked up on the switch instead, chances are your opponent just went into a faster mon and is about to fire blast your ass.