Apart from the obvious but can you use a Hot Glue Gun to glue styrene and other rollingstock parts together and what is best glue you can use for glue.

Yes I know there is modelling glues and unlimited brands but which are actually the best brands.  

Thanks in advance.

There is almost no situation where a hot glue gun is better than another more appropriate adhesive to do any job. Certainly not for polystyrene, it requires an adhesive that is actually a solvent for the polystyrene, melting it slightly to perform a weld.

Apart from the unsuitability, a hot glue gun is likely to damage many plastic items due to the heat of the process.

I think the OP has seen some videos Woodland Scenic's done where they use a hot glue gun on foam. But a HGG is bad for foam! Not the one they sell, as apparently it's more of a warm glue gun with a much more foam friendly operating temperature

http://youtu.be/K3DBgA0TtYo

As for plastic glues, I've used a mix. My default standby is Revell Contacta, but lately I've been favouring Tamiya Limonene and their ABS cement for the odd kit made from ABS plastic.
It's typically been superglues that give me the most problems with the only reliable ones I've found coming from Army Painter or Zap - though that changes depending on the batch. A recent bottle of their thick CA which has a slow grab time, actually functioned in the reverse upon contact with the resin Blue and Gold models use. It's making assembly of their goods shed interesting.

There is no such thing as one glue does all unfortunately and the list of glues and liquids is quite long actually. Each type of plastic usually has its own glue specially made to glue that plastic, however some will work on other plastics though and not all plastics can be glued Delrin type plastic is one such plastic no known glue will successfully hold things made from Delrin together indeed it may need to be joined by a mechanical type joint. This plastic is mainly used in bogies etc though. ABS is used for some bodies of rollingstock though and this requires a glue suitable for ABS. So you can see you have to get a glue that is suitable for the job at hand and this is were it pays to look at a glue container and read what it will glue and what it wont glue.

Tube glues work differently to liquid glues though, a glue in a tube usually just holds the two pieces together but does not fuse them together there are exceptions to this though, A liquid glue like MEK for example will fuse two pieces of the same type of material in this case styrene together, so they are virtually unable to be separated in the future! Tetra is also good for this but goes off pretty quickly, good if you want to finish a model fast though!

PVA glue is good for wood and things, Super Glue is good for Resin kits or even whitemetal, paste is good for cardboard or paper, you could go on listing these things for ever actually.

not all plastics can be glued Delrin type plastic is one such plastic no known glue will successfully hold things made from Delrin together

I was discussing this with a 'colleague' today, there are 'glues' for Delrin, they're just not known to you.

I have been looking at the production process and chemistry of Delrin and I know methyl benzene is a solvent to Delrin, and I will have to revisit it, but I also believe now that MEK may be a solvent for Delrin too.

As for adhesives for Delrin, there are several, phenoweld is one and there are several epoxy variants too.

Tube glues work differently to liquid glues though

What are tube glues and liquid glues? Serious question! I buy CA glue in a tube, but it's a liquid, and where does caulk fit?

Tube and liquid glues do not work differently if they are the same glue, the tube glue is just thicker. This is for a reason, plastic solvent tubes are for plastic modelling locator pegs, which you may not really want anyway.

No-one uses hot glue for plastics modelling. Nor for joining plastic to other substances. You're looking for either a binary epoxy or cyanoacrylate ester, eg. Loctite 401.

I have been looking at the production process and chemistry of Delrin and I know methyl benzene is a solvent to Delrin, and I will have to revisit it, but I also believe now that MEK may be a solvent for Delrin too.

I have tried immersing Delrin (Acetal) in MEK and the MEK does not touch it. Although it is quite nasty, MEK is still probably the best glue for polystyrene.

Yeah, and I still not had the time to look at it myself, I have always considered MEK to not be effective on Delrin, but when I was looking at the chemistry I saw structural features that made me think that I had to revisit MEK. I wonder if true DuPont Delrin is slightly different to everyone else's acetal, I am going to have to somehow track down some genuine Delrin and test it and if it does not dissolve in MEK I am going to have to go back and revisit some of my chem learnings...

My only success at gluing Delrin has been with Selleys Plastics Glue http://www.selleys.com.au/adhesives/household-adhesive/quick-fix-adhesive/plastics-glue/