I plug things quite often, mainly because it is relatively similar to IM with a lot of drugs I use (particularly morphine, midazolam & methoxetamine) but doesn't involve the same level of hassle.
My grand discovery is the 16 gauge drawing needle- I get them with wheel filters from the needle bank. These are absolutely perfect for plugging- they are a needle without a point that is about 1.5" long and about as thick as a medium sized nail. It makes it much easier to plug as you don't have to shove such a large thing up yer ass (it's considerly smaller than an oral syringe or even an 1cc barrel) and doesn't require lube, so you don't have to deal with a lubey asshole as you're rocketing into another dimension.
I have also found that if you're plugging pills it's worth actually extracting/filtering them properly. Although there is no reason you can't plug inert materials, clean solutions just seem to kick in faster and very slightly stronger. I presume it maximises the surface area.