A very old way of measuring viscosity is to measure time which require for a heavy ball (glass, steel, ceramic) to travel a certain distance through the liquid (in your case glue). Do search on "Stokes' law viscosity". You can perform the test in closed tube or cylinder to reduce solvent evaporation, and you can also stabilize temperature by placing the closed tube with the sample into thermostat. If you do not have thermostat, you can use ice/water bath which gives you 0 C, or buy one from pet store which is used for fish tanks. And of course check Yellow Pages you may find a used lab equipment shop, which will sell it to you for $100-200.