Can I use multiple resistors is series to approximate a precision resistor called for in schematic?
This approach works well for 'one-off' instruments designed to work at room temperature. I use it all the time. It has two drawbacks.

1) It's labour intensive, which is why it's not used for mass produced equipment, where it's cheaper to buy 0.1% resistors and just fit them, rather than muck about measuring and matching.

2) 1% resistors won't necessarily have as good a tempco of resistance as 'precision' 0.1% or 0.01% resistors. This will be mitigated to some extent if you are only after tracking between multiple resistors, but even then there is no guarrantee cheaper resistors will track well. A set of precision resistors in a pack will be specified to track to a certain extent.