Do 90 - acute wind angle then use clock analogy to get headwind/tailwind component.
E.g. Track is 180
Wind is 240/30. So 90 - 60 = 30
30, so take half of the windspeed, gets headwind component of 15kts.
Hence, groundspeed for planning on this leg is IAS - 15kts (say 75kts for average GA ac).
To work out fix times, do simple leg distance / groundspeed calc.
E.g 42nm leg = 42/75 x 60 = 36 mins
Then work out proportional distances/times to fixes on the leg, ideally at some good fraction like 1/4 or 1/3 way along.
I don't think you have to bother about temp. differences etc.. on the IAS