I have tried a couple of different things.
Start by entering the recipe intor beersmith and adjust the hops by either:
1. Take note of the IBU for each addition, add 15 mins to each hop addition on beersmith, and adjust the amount of hops added to achieve the desired level of IBUs. When you brew, make the additions at the usual times (ie. 75min addition = 60 min addition)
2. Brew as usual, but subtract 15 mins from the addition. Ie. 60 min, becomes 45 min, 20 min becomes 5 min, and flameout... well try the french press method: (as described to me by Brendo)
From about halfway towards the end of fermentation, take however much hops you want, and steep in a (clean) coffee plunger with 500mL of boiling water for 5-10 mins, plunge and pour straight into the fermenter. Pour another 500mL of boiling water into the coffee plunger, steeping for one minute this time, then straight into the fermenter. These become flavour and aroma additions.
You can get away with just a bittering addition at 45 minutes when no-chilling. I have had the most success using the second method. I have doen a few the first way, and have found that the brews tend to be under-hopped.
I just brewed an all cascade APA and, by memory I did a 45min (60), 0 min (15) addition during the boil and french pressed as described above for 5 mins and 1 min. It hit the level of hoppinness I was after perfectly IMO.