Be careful what brand and product you buy (solvent), not all lighter fluid works, check the MSDS and try asking/checking around to see if it's safe, most people on this site would be glad to keep another member alive

The amount shouldn't change when dealing with the solvent, the lye isn't too hard to find, look for drain cleaners that are in powder/crystal form, and check that they are ONE HUNDRED PERCENT sodium hydroxide (lye). If they are only say, 95%, you're smoking/intaking residues and potentially chemicals that can eat away at you (hey, they were meant to go down the drain!). Drano has no products that are 100% lye, look out for rootol (mis-spelling?)
If the lye/acid is not already pre-measured in the teks, look into pH, and pH papers to measure how much lye or acids to use.