Before I fished Virginia at Earith I spent 2 days feature finding and pre-baiting.
I mapped out the whole lake for myself and @brucelait, I know I had a hand drawn copy, I think we had one each.
Over 2 years I had a total of 4 blanks, and 2 of them were when the lake froze over while I was fishing.
I can't remember how many fish we had, but it was hundreds and many were over 20lb.
It's not that hard.
If you want full depths and distances then a float and lead, if you are happy with just 'rough' then a lead alone.
Use braid to a 30lb mono ( Amnesia) shockleader for a better feel, with a run ring and 3 or 4oz lead (maybe a lead link), and a marker float at the end.
Obviously cast out and feel around; gravel feels 'bumpy', sand is smooth, clay often a bounce as the lead comes free then slides smoothly, silt is the lead pulls free, but slides slowly. Weed almost pulls back, jams, comes through, sticks, and repeat.
Hold the line tight down, then pull a foot of line off the reel at a time until the float reaches the surface. Weed might stop it, even with a lead link.
If you use just a lead you are counting it down from the cast, I've always used roughly a metre a second, but it won't 'donk' on or in silt or weed. You then have to clip up once you find the spot and get the distance on sticks or walking it out.
I can't remember who said it, I think Dave Lane, mono is a smoother cast, and on distance sticks I think recommended taking a wrap off for the fishing rods. So if you got 15wraps with the marker rod and braid, go 14 with mono on your fishing rods.