Very simple!
Have your decoder and a monitor screen close by. Set your decoder to beep when the sat is hit, Input the 8w tp first lest you bypass 5w. Use this one 3926v 30000 (I assume its Cband that you target just by the mere mention of 18 w.
Then while on the back of your 8footer, lift your dish up slowly by like 3-4 inches and you will start hearing the beeping BPM increases, then azimuth your dish to the right a bit and you will hit the green high. That way you know you are close to 5w. And at this juncture I can attest 8w is far better for cband than 5w.
Alright. Once your are there, input this tp. 3712 V 4250 for crtv then elevate your dish slowly again for like an inch and your are there!
NB.
When you are on 8 west. It's possible you may hit that signal high but if you by interest would like to scan it may not yield any channel, if that the case turn the dielectric bar on the other marks whether cutting between the lnb iner probes or the other way.