Grateful for confirmation on the below. You'll have to forgive me as my mind is still addled from pain meds at the moment.

So I was in a wooded area, advanced the act deck so the cultists and ritual site appeared. There were 3 cultists, 1 with 3 hp, the others with 4. I chucked dynamite into the main path killing one. On the next round I spent one action to move to the main path, shot one cultist, stabbed the other. Agenda advanced so that Umordhoth spawned at the ritual site.

At this point doom tokens don't do anything right? So i spent a few turns loading up on resource tokens and equipping good weapons /allies. Was this okay to do? It seemed a bit to easy on me, as I ran into Umordhoth shot him twice, took a hit (redirecting some damage to Lita) then shot him twice more "killing him" (vicious blow was in there somewhere).

Just wanted to check I didn't miss anything that should have stopped me loading up before fighting the big bad? Cheers!

Doom counters don't mean anything once the big U spawns, but he his a Hunter. So you don't have several turns. At most 2 before he moved into your location.

There we go, read up on massive, and missed Hunter! Again, I blame the drugs! I probably would've moved away to get a few rounds of prep in, but yeah, thought it was too good to be true. Thanks man