The problem is getting staples into MDF so that they hold. Alternatives would be to use the small cable clamps with screws (you would need to pre-drill), or you could use heavy duty velcro.

I prefer forward action staplers (the staple exits the stapler from the end where force is applied), opposite of the original Arrow stapler design.  Here's a link to a Klein Tools Cable Stapler that accepts staples for different sizes of wire.

I think your bigger long term issue is going to be using MDF.  It has a tendency to flake off when staples are driven into it, and even worse will eventually warp and sag in between its framing supports.  This will likely lead to issues with uneven track, switch binding, and derailments.

Though more expensive a decent quality plywood will be worth the extra expense in the longer term.

Should just be able to use round crown wire staples.
Something like this will do the job.

https://www.homedepot.com/p/Ar...le-Gun-T25/100091191

Agree with MDF being a problem for a number of reasons, including holding fasteners. You may be better off sticking the wires onto it with 2 sided tape or hot glue blobs.

If you think you have problems now, wait until you add scenery to MDF. The water will make it twist and warp, and possibly collapse.

I’m getting the strong message I should rethink using the MDF! Thanks for the tips all.

@BenLMaggi posted:

If you think you have problems now, wait until you add scenery to MDF. The water will make it twist and warp, and possibly collapse.

Ben,

I disagree.

Particle Board, Yes.

Real MDF, No.  '

Real world road signs are made out of MDO, which is MDF with a paintable surface.  Since they withstand weather just fine MDF should have no problem with a little water during construction.

Staples are another story, and indeed could be a problem.

Mike 

I have used MDF forever. Never had issue with either staples holding or water features warping, Use longer staples. If your water features are warping your MDF you're not prepping correctly. And if we are talking about wetting the MDF with glue etc for scenery, you're using too much glue. Nothing wrong with MDF.

Look for

Holiday Light Tacker Staple Gun by Surebonder

It uses staples that have a "hump" in the center and plastic saddles to grip small diameter wire without cutting into it.  As the name implies, it was specifically designed to affix decorative light strings.

I'd post a link, but, since the company is not a sponsor, I'd probably get in trouble.

usually wire ties and a flat clip; staples are hard to remove.

Thank you AlanRail and palallin. I appreciate everyone’s response.