Is the Smiths Machine the one that you can fly forwards or backwards? This has been a learning curve for me. At 40odd it has taken my muscles quite a long time to start working well again and now only just starting to reap some gains after 2 years of slog. Also technique is most important so taken a while to workout what works for me and learning every day I go just watching what others do and then trying that out.
Good work for getting back into the gym mate.
A tip I can pass onto you is that remember whilst choosing your exercises and most importantly your technique and form, that natural movement is key.
Alot of people hyper extend their limbs whilst doing an exercise which is both dangerous (for injuries) and unnecessary, i.e. bench press, arms should come down to 45 degrees (upper arm and forearm at right angles) which should leave the bar a good 4 inches or so (depending on your body) off your chest. See alot of people loading up huge weight and letting the bar hit their chest, by which time their arms/shoulders are hyper extended.
One revolutionary point that will transform your workout if your not doing it already, is whilst doing any exercise, (don't swing - obvious point) keep the weight fully on your muscles at all times during the set (don't let the weight hang and the muscle group the exercise focuses on, rest whilst in the middle of reps). I.e. bicep curl, through the 8 reps, make sure your bicep is controlling/holding the weight the whole time throughout the set.
Also at the end of each rep, hold the weigh for 1-2 seconds and have emphasis on your negative reps.
Forgive me if you knew any of this, trying to be helpful
Smith's Machine is below.